C-17s for the IAF?

[Rahul M]

To be a fair comparison, you need to compare the C-17 and Il-76 at equal payloads and see how the landing lengths compare.

in that case why buy the much costlier C-17 in the first place ?

[GeorgeWelch]

To be a fair comparison, you need to compare the C-17 and Il-76 at equal payloads and see how the landing lengths compare.

in that case why buy the much costlier C-17 in the first place ?

Because the C-17 might have a shorter landing distance than the Il-76 with the same payload?

On the other hand, if you do need more payload than the Il-76, whining about any extra distance than the Il-76 seems pointless. If you need more you need more regardless.

[Gilles]

The other point you're missing Gilles is that the quoted landing lengths are at a weight of 447,000 pounds, or 164,500 pounds of fuel and cargo.

Many missions won't require that much payload.

Decrease the weight and the landing length decreases.

To be a fair comparison, you need to compare the C-17 and Il-76 at equal payloads and see how the landing lengths compare.

If flying tanks in are the whole idea, like some have stated (I don't know if its true, I'm just quoting), and assuming an Indian MBT weighs 135000 lbs (Wild guess) , that leaves 30,0000 lbs for fuel. This aircrat burns around 18,000 an hour of fuel. I dont see how much weight can be saved.

[Katare]

Gilles,

What's the point of your constant questioning of "unpaved runway" capabilities of C17? It's a huge aircraft designed for certain purposes for certain customers. The customer would verify if the aircraft meets its needs on its airfields and supplier would have to not only demonstrate but also guarantee those performances. A generic discussion of aircraft's capabilities is useful, hypothetic specifics are beyond the means of internet jingos.

Everyone on this board loves Il76 and we all would love to have more of them in IAF. I am having hard time understanding the logic behind your jihad against anything C17?

Its useless exercise for enthusiasts like you & me to figure out (armed with mighty google) if a C17 can land in certain airfield in India with a tank in its belly.

[chetak]

quote="GeorgeWelch" quote="Rahul M"
To be a fair comparison, you need to compare the C-17 and Il-76 at equal payloads and see how the landing lengths compare.
in that case why buy the much costlier C-17 in the first place ?

Because the C-17 might have a shorter landing distance than the Il-76 with the same payload?

On the other hand, if you do need more payload than the Il-76, whining about any extra distance than the Il-76 seems pointless. If you need more you need more regardless.

Anyone who has watched an IL-76 take off in India would not have failed to notice the laboured and flat climbout that the aircraft often performs with any significant load .

In russia, fully loaded it takes off like a rocket.

Its down to the laws of physics and engine performance at higher temperatures.

What makes you think that the C-17 is going to do any better?

Its certainly not carrying any heavy MBT.

The C-17 just cannot carry the its glossy brochure stated figures or even perform anywhere close to what quoted therein. Just like the IL-76, it also will have a degraded performance, in Indian conditions.

Rough field capabilities of the IL-76 have been amply demonstrated and is definitely better than the C-17.


Its sure that the C-17 will carry a bit more than the IL-76 in Indian conditions but that "bit more" does not justify a massive investment.

The IAF already has large infrastructure to operate the IL-76.

Makes sense to just go in for more of the same aircraft.

[GeorgeWelch]

If flying tanks in are the whole idea

If flying tanks is the idea, then it doesn't matter because the C-17 is the only game in town.

[rohitvats]

Gilles,

What's the point of your constant questioning of "unpaved runway" capabilities of C17? It's a huge aircraft designed for certain purposes for certain customers...............Its useless exercise for enthusiasts like you & me to figure out (armed with mighty google) if a C17 can land in certain airfield in India with a tank in its belly.

The reason for the debate on STOL capability is that it has been listed as an USP of C-17 and various numbers bandied about. GeorgeWelch' s nitpicking not withstanding, it is a fact that this STOL capability is doubtful and comes with lots of ifs and buts. The aircraft seems to run into acquisition issues every where it has been bought (except in ME). Another point, a news article quoted an IAF officer about the virtues and requirement of STOL and how C-17 fit the bill. I personally think that the quote is a case of DDMitis. We're simply trying to demistify this STOL and what benefit, if any will it provide to end user.

IMO, the STOL in our case is not a requirement (at least not a deal clincher). The Thoise and Leh AB can take biggest of airliner and C-17 will be not a problem. IL-76 has yet not landed (public information) on an ALG and I don't know how C-17 is going to do it. Even though, these (Fukche) are 9000+ feet airstrips. There are two definite advantages to C-17: Carry outsize cargo (T-90/Arjun) and even with degraded performace, carry more load than an IL-76.

...............Its certainly not carrying any heavy MBT.

The C-17 just cannot carry the its glossy brochure stated figures or even perform anywhere close to what quoted therein. Just like the IL-76, it also will have a degraded performance, in Indian conditions. Rough field capabilities of the IL-76 have been amply demonstrated and is definitely better than the C-17.
Its sure that the C-17 will carry a bit more than the IL-76 in Indian conditions but that "bit more" does not justify a massive investment. The IAF already has large infrastructure to operate the IL-76.Makes sense to just go in for more of the same aircraft.

Actually, it is going to be the only a/c to be able to carry a MBT. As for degraded performace, if IL-76 can airlift a T-72 to Leh/Thoise, C-17 should have no problem at all. But yes, apart from carrying outs size caego, your assertion for having more Il-76 is correct.

Only C-17 can do this:

[GeorgeWelch]

Anyone who has watched an IL-76 take off in India would not have failed to notice the laboured and flat climbout that the aircraft often performs with any significant load .

In russia, fully loaded it takes off like a rocket.

Its down to the laws of physics and engine performance at higher temperatures.

What makes you think that the C-17 is going to do any better?

Its certainly not carrying any heavy MBT.

Because a MBT isn't near the the max capability of the C-17 so it has a lot of extra margin.

Its sure that the C-17 will carry a bit more than the IL-76 in Indian conditions but that "bit more" does not justify a massive investment.

Except there are some things the Il-76 simply can't do.

Also if that 'bit more' is the difference between being able to do the job or not, it makes all the difference in the world.

The IAF already has large infrastructure to operate the IL-76.

Makes sense to just go in for more of the same aircraft.

Except it wouldn't be the same aircraft. New engines especially are major maintenance difference.

[vasu_ray]

there are light tanks, if they can hold against the Chinese MBTs (ATGMs are far more effective), an IL-76 can fly one while the C-17 can fly two of them

10 nos of C-17 isn't a significant airlift capability if Chinese tank nos are to be faced

[GeorgeWelch]

GeorgeWelch' s nitpicking not withstanding

Nitpicking? Gilles made an absolutely stupendous claim ('there are no unpaved runways in Australia that can accommodate the C-17') and I called him on it.

it is a fact that this STOL capability is doubtful and comes with lots of ifs and buts.

There is nothing doubtful about it. If you need to do it, you can do it, as Gilles himself has admitted.

The aircraft seems to run into acquisition issues every where it has been bought (except in ME)

It is an expensive plane so there will always be fights about that much money, but there have been no actual procurement issues for foreign customers. They have always come on time and on budget.

IMO, the STOL in our case is not a requirement (at least not a deal clincher). The Thoise and Leh AB can take biggest of airliner and C-17 will be not a problem.

I think you are right with this. STOL is a nice bonus, but I think the C-17 sells itself on just 'regular' cargo missions.

As for degraded performace, if IL-76 can airlift a T-72 to Leh/Thoise, C-17 should have no problem at all.

Actually, I doubt if an Il-76 could airlift a T-72 to Thoise.

If you recall the Bofors to Thoise article, that was a 34 ton payload and they could only land if the temperature was 15C or less!

T-72 is 45 tons.

[Victor]

Makes sense to just go in for more of the same aircraft.

Obviously, "the same aircraft" cannot do what the C17 can for the IAF's specific needs right now. Whether political or military, I don't expect them to spell out in detail what those needs are for the benefit of Internet chAirmarshals like us and neither do I consider the whole system to be rotten. IMO, it would be more productive and interesting for us here to try and discuss why the C17 is being chosen given all the obvious facts instead of suggesting that the IAF and GoI are stupid and may be acting against India's interests.

[rohitvats]

there are light tanks, if they can hold against the Chinese MBTs (ATGMs are far more effective), an IL-76 can fly one while the C-17 can fly two of them

10 nos of C-17 isn't a significant airlift capability if Chinese tank nos are to be faced

The only true challenge to an enemy's MBT is your own. Period. The light tanks will be fried if they take on the Chinese MBT.

As for the number of C-17 and their MBT carrying capacity, these are not, IMHO, means to help in reacting to situations along the LAC. Capability to airlift a MBT as in contingency (Sri Lanka), power projection or trying to quickly respond to unexpected situation (airlift of part of 6th Mountain Division during Kargil) is a different ball game. In case of China,we know where we are going to fight them and can pre-position the required assets (Armored Regiments in this case). Relying solely on C-17 for doing this in case of war is a non starter.

[vasu_ray]

ok, two things come out

1) flying an MBT to an ALG isn't a practical requirement for IAF

2) IL-76/C-17 can do a lot better in payload terms during night flying (low temperatures), C-17 being modern has better night landing equipment including flying in bad weather, its only a matter of equipping ALGs

[rohitvats]

Nitpicking? Gilles made an absolutely stupendous claim ('there are no unpaved runways in Australia that can accommodate the C-17') and I called him on it.

There is nothing doubtful about it. If you need to do it, you can do it, as Gilles himself has admitted.

George, I am actually disinclined to get into debate on this one. When I look at unpaved runway performace, I look at C-130 and our ALGs in different parts of India. War is an extreme situation and one's got to do what needs to be done. But having said that, having a dedicated team of Engineers to look after the airstrip after the C-17 sorties is not someting I will call ideal. Our ALGs are in forward areas and would be under enemy shelling (ladakh) form word go. IA cannot be bothered, unless in dire straits, to try and keep them active in such situation. We would have pre positioned every thing in advance.

It is an expensive plane so there will always be fights about that much money, but there have been no actual procurement issues for foreign customers. They have always come on time and on budget.

It is with respect to the roles they were supposed to fulfill and how the much bandied about capabilities haven't either been used have not been usefull at all. Case in point is Canada paying 118million USD for leasing IL-76 versus paying billions of dollars for C-17s.

I think you are right with this. STOL is a nice bonus, but I think the C-17 sells itself on just 'regular' cargo missions.

Agree on this.

Actually, I doubt if an Il-76 could airlift a T-72 to Thoise. If you recall the Bofors to Thoise article, that was a 34 ton payload and they could only land if the temperature was 15C or less! T-72 is 45 tons.

Please read the same section again. It describes the experience of carrying T-72 to Leh/Thoise and Srilanka by the same officer(Group Captain Bewoor). And weight btw is 43 tons.

[GeorgeWelch]

Please read the same section again. It describes the experience of carrying T-72 to Leh/Thoise and Srilanka by the same officer(Group Captain Bewoor).

Maybe I'm missing it, but I only see Leh, not Thoise.

And weight btw is 43 tons.

I think we have some confusion over tons and tonnes.

[GeorgeWelch]

Also I should point out that the operations document posted by Gilles is outdated.

It was overly conservative and new tests have help push up landing weights and decrease required landing lengths.

http://www.amc.af.mil/news/story.asp?id=123169693

"The C-17 SPRO test results will translate into expanded capability since rainy or wet weather conditions won't be such a limiting factor at austere locations with semi-prepared or dirt runways," said Major Hill.

. . .

The test evaluated how C-17s can fly into more restrictive locations and areas under varying weather conditions in an effort to best meet the needs of the warfighter as well as providing rapid response at home and abroad in response to humanitarian relief operations, Colonel Scorsone said.

Testing also evaluated C-17 takeoffs and landings in dry and various wet conditions, and increased the aircraft's operating weight capacity by 41,000 pounds.

. . .
Before this test, if any moisture was present on the dirt strip, ground personnel had to use an overly restrictive RCR rating of four which significantly limited the C-17's flexibility.

[Kartik]

Makes sense to just go in for more of the same aircraft.

Obviously, "the same aircraft" cannot do what the C17 can for the IAF's specific needs right now. Whether political or military, I don't expect them to spell out in detail what those needs are for the benefit of Internet chAirmarshals like us and neither do I consider the whole system to be rotten. IMO, it would be more productive and interesting for us here to try and discuss why the C17 is being chosen given all the obvious facts instead of suggesting that the IAF and GoI are stupid and may be acting against India's interests.

well said Victor. its getting tiring reading about how the IAF is now all of a sudden bitten by the brochure bug and that all the politicians making the decisions (with inputs from the IAF) are being blackmailed by the US or being bribed, or their children are being sent to the US. people are overlooking how, despite the fact that the IAF operates the IL-76 and IL-78 and know the pros and cons of these aircraft in and out, they are more interested in buying the costlier C-17 and the A-330 MRTT- it would appear that some people here seem to think that they're simply dumber than the average BRFite or willing to sell the country, which is really not fair. or that some BRF forumers know every operational scenario the IAF will ever face and cannot fathom why the IAF and GoI would want to spend any more to induct these fancy "white elephants"..the attitude is to just conveniently ignore that no IL-76 variant can carry the T-90 or the Arjun because after all when are we going to do it ?

surely the IAF has drawn a list of what it wants its transport fleet to do and assigns certain weightage to each of those points in the list based on their priority, does anyone on BRF know how many points they assign to the ability to transport outsize loads to places like Leh or Thoise ? no. so its useless to suggest that they simply buy more IL-76s or its future variants. they must be looking at the C-17 for a reason, otherwise it would be impossible to justify to the beancounters at MoD that these aircraft are worthwhile to purchase.

as retd. Admiral Arun Prakash wrote in an article (published in Force, so not possible to reproduce here), most Russian equipment was inducted based on what the Russians offered, followed by the GoI sending some officials to evaluate, and even with faithfully filed evaluation reports by IAF officers it really didn't make much difference, because the decision was already made by the GoI. In those days the IAF made the best of what it was given- it didn't have to be the best equipment around the world or best fit for the IAF's specific needs. today the scenario is different and they can make a choice by evaluating their options and choosing the one that best fits their needs or future projections. a large portion of BRF seems to filled with those whose opinion is that they know better than the IAF or that they're incompetent or even worse, just to be interested in a US aircraft (the primary reason for most being simply that its American). I wouldn't even care if the C-17 were rejected by the IAF if they found that it didn't fit their bill or their needs as long as they found something else that did fit. Most posters on BRF are on the contrary suggesting that the IAF make do with limited capabilities rather than spending money on a small fleet to fill a specific niche that no IL-76 can fill.

On a different note, the South Africans, now that they've cancelled their A400M contract are speaking of interest in a mixed fleet of C-17s and C-130Js. they say that to carry the tonnage they require to carry only with C-130Js, they'd need a large fleet that would cost as much as the much smaller A-400M fleet would cost. so, they'll likely split their purchase between the two C-130J and the C-17. even France was reportedly looking at the C-17 due to massive delays in the A400M program along with huge cost escalations.

[Manish_Sharma]

Gilles,

What's the point of your constant questioning of "unpaved runway" capabilities of C17? It's a huge aircraft designed for certain purposes for certain customers. The customer would verify if the aircraft meets its needs on its airfields and supplier would have to not only demonstrate but also guarantee those performances. A generic discussion of aircraft's capabilities is useful, hypothetic specifics are beyond the means of internet jingos.

Everyone on this board loves Il76 and we all would love to have more of them in IAF. I am having hard time understanding the logic behind your jihad against anything C17?

Its useless exercise for enthusiasts like you & me to figure out (armed with mighty google) if a C17 can land in certain airfield in India with a tank in its belly.

But Katare the points are valid, at 5 times the cost of Il 76, without this debate we would not have know the 3500feet + 300 + 300 feet lacuna played by boeing even with US army, not to mention this megafast deals signed with US, I mean take Hawk Jet Trainer thing for last 26 years, on top of that how this Raytheon having MOD file was suppressed do ask for debate. And so much is coming out of this Manthan!

[Brando]

surely the IAF has drawn a list of what it wants its transport fleet to do and assigns certain weightage to each of those points in the list based on their priority, does anyone on BRF know how many points they assign to the ability to transport outsize loads to places like Leh or Thoise ? no. so its useless to suggest that they simply buy more IL-76s or its future variants. they must be looking at the C-17 for a reason, otherwise it would be impossible to justify to the beancounters at MoD that these aircraft are worthwhile to purchase.

So you are saying that Indians should trust the IAF and the GOI implicitly to do the right thing and trust that they spend $2.5 billion dollars of taxpayer money without so much as a by or leave, especially after all the controversy that the C17 has generated in the West ? That would be appropriate in a COMMUNIST country.
The $2.5 odd billion dollars is not a small sum in a country like India to cavalierly trust the government. While there might be numerous other defense expenditures and deals that the public would have no way to properly vet, at least in the few cases where there is adequate public information, it is only prudent and wise to question ALL angles of such an expensive purchase be they technical, political or criminal. As for the beancounters, they usually catch the crime after the fact. I could easily argue that with the same $2.5 odd billion dollars, the GOI could easily build an all-weather railway and motorway to both Leh and Tawang that could ship more men and material than the C17 ever could.All this however doesn't mean that the C17 is not a good choice or that there are some nefarious motives behind its acquisition, it merely implies that I hold dear Ronald Regan's favorite Russian phrase " Trust but Verify".

[Victor]

So you are saying that Indians should trust the IAF and the GOI implicitly to do the right thing and trust that they...

I cannot believe I'm reading this on BR, even if we don't collectively amount to a fly's f@rt in influencing any defence purchase or IAF doctrine.

Let me try again: If we do trust the GoI and IAF (and I believe that we should and must, if only because we are really irrelevant and don't come anywhere close to having the needed information), then there must be a very urgent need for the C17 and only the C17.

[shiv]

Hasn't the IA recently asked for a tender for a 100 "light tanks" for the mountainous regions? Perhaps they want to put 4 tanks apiece in that C 17?

[Kanson]

These "18 inch rut" stories are all related to Semi-prepared runway which are unstablised. There is as such no problem with paved runway or Stabilised semi-prepared runway. As i know, most of our ALGs are stabilised semi-prepared runways ex. DBO.

Its all a matter of how strongly the runway was built. Like I said, the C-17 has the footprint of a Boeing 707. How many unpaved runways in the world do you think were built with hosting a large airliner in mind? The footprint of the C-17 is similar to other airliners of its weight category. A Boeing 777-200, at 247,000Kg, is about the same weight as the C-17 and has the same number of wheels (14, although with a different geometry). Do you think any of the ALGs as they are now, can support the weight of the B-777-200?

I do not know about High Altitude performance, about carrying the new tanks, or about required runway length, but there is not a shadow of a doubt that the IL-76 can land in much softer runways than the C-17 can.

I agree you may be right. The question here has to be asked is what payload IAF wants to carry to where and on which runway. What is the Ops requirement. Probably that will dictate all our discussions. Beocz the question about the payload dictates the weight category of the a/c and thereupon the landings on softer runways.

For comparison of payload and MTOW changes:(from wiki)

Payload: 48,000 kg (Il-76M/T), 50,000 kg (Il-76MD/TD), 60,000 kg (Il-76MF/TF) and 77,519 kg (C-17)
MTOW: 170,000 kg (Il-76M/T), 190,000 kg (Il-76MD/TD), 210,000 kg (Il-76MF/TF) and 265,350 kg(C-17)

So it is not going to be the question of Il-76 or C-17 when dealing with softer runways. Becoz with heavier payload Il-76 comes under heavier category. Question is what payload to where ?
If IAF is convinced of greater payload, the requirements of better runways could be taken care of.

-------------------
Regarding High altitude performance, the following i scoured from net.

Altitude with 60 000 kg payload:
11 171 m

Altitude with 70 000 kg payload:
9 805 m

Greatest mass carried to height of 2000 m:
73 039 kg

[Singha]

unless the ALGs are expanded and improved, flying in C17 class ac with reduced payload may not be
cost effective vs a C130 class smaller bird with a full belly.

[geeth]

>>>Tyre Pressure ??

I haven't touched a book on Aeronautics for almost 3 decades.. Hardly anything remains in my head now. However, from whatever little is still retained, I can recollect that tyre pressure is a major factor which determines the pressure exerted by an a/c on the runway.

The tyre pressure in a/c wheels are way above that in automobiles. Basic reason is to reduce the size of the tyre>>weight>>volome. In ideal condition, the contact area that a tyre makes with a flat surface is an ellipse. So, to reduce pressure on surface, one can increase the size of the tyre, or reduce the pressure inside the tyre. When you reduce the pressure inside, the tyre is more pressed down, thereby increasing the contact area (this increases friction ofcourse).

From Google I could see the max tyre pressure for IL-76 is 5 bar - 75 PSi. Now I find that for C-17, the tyre pressure is almost double that. In such a scenario, I wonder how will it affect its performance on semi / unprepared surface. I can't recall what other factors affect the runway surface, but tyre pressure is an important factor.

Often, overloaded trucks 'plough' through well maintained roads, because the tyre pressure exceeds the design limit for the road. Multi Axle vehicles is the answer, if you want to carry heavy loads. It is important to maintain correct tyre pressure in your car - more will lead to slippage and less will increase friction leading to less mileage in either case.

NB: Filling Nitrogen in your car tyre improves performance - it maintains the pressure for about 45 days without much deviation, reduces punctures, improves mileage a bit. Filling each tyre initially costs Rs 50/, subsequent top ups Rs 10/tyre. It is worth a try, IMO.

[vasu_ray]

C-17B comes with these, probably due to field experience and systems advancement

"The package includes higher thrust engines and double-slotted flaps for "extreme" short-field landings adding a centre main landing gear with tyre inflation and deflation an engine-out control system (EOCS) a precision landing augmentation system (PLAS) an all-weather, autonomous landing system (AALG) an opportune landing site (OLS) system and the advanced situational awareness and countermeasures system (ASACMS)"

one can only say the upgrades would cost stupendous amounts and the current purchase price is just the start

[Gilles]

C-17B comes with these, probably due to field experience and systems advancement

"The package includes higher thrust engines and double-slotted flaps for "extreme" short-field landings adding a centre main landing gear with tyre inflation and deflation an engine-out control system (EOCS) a precision landing augmentation system (PLAS) an all-weather, autonomous landing system (AALG) an opportune landing site (OLS) system and the advanced situational awareness and countermeasures system (ASACMS)"

one can only say the upgrades would cost stupendous amounts and the current purchase price is just the start

And most of this is to meet the performance targets that the original C-17 was supposed to have in the first place.

The flaps will allow slower approach and landing speed.
The extra center gear will reduce the aircraft's ACN and improve wheel braking
The tire deflation system will do the same.

Not certain about the EOCS but it may be this:
We've talked about landing distance but there are also take-off issues.
One issue that increases the required take-off runway length of this aircraft is VMCG. It is the minimum speed at which an aircraft can maintain directional control on the ground with an engine out, and with the three others engines at take-off power (when the rudder begins to have enough airflow to help the nose steering counteract the assymetrical thrust). Until that speed is reached, an engine failure means an automatic aborted take-off, otherwise it ends up in the ditch on the side of the failed engine. Because that speed is relatively high in the C-17, one must plan for enough runway to be left in front in case of an abort at VMCG minus 1 Knot.
I think that on the C-17, the VMCG is almost the same as V-2 (take-off speed). So if its powerful enough to take-off in 2000 feet, but that VMCG is only reached at 1900 feet, if an engine failure is reached just before VMCG, the required take off runway will be 1900 feet minus 1 + distance required to stop it from there.
If engine failure occurs at or above VMCG take can be continued if speed is above V2.

I suspect (just a wild guess) that EOCS is an attempt at lowering the C-17s VMCG (and thus reducing its required take-off runway length)

All this to say that it is not because one demonstrates a 2000 foot take-off on a long runway that it can take off from a 2000 foot runway. Its like a magician who pulls the bunny from the hat. You see him do it, but did he create a rabbit out of thin air or did he give you the illusion he did it ?

But of course some people will say : "In war, who cares about losing an engine on take-off ?"

Many things happen in war that don't occur in day to day life. For one thing, magicians make bunnies out of thin air..........

[Juggi G]

Offset policy inertia curbs Thales-Samtel JV
Business Standard

[GeorgeWelch]

And most of this is to meet the performance targets that the original C-17 was supposed to have in the first place.

No, it's to make the C-17 even better, but the USAF has determined that the C-17 is good enough as-is and thus C-17B is dead. There was never a real demand for the C-17B, it was just a Boeing proposal to drum up more sales.

If the C-17 was as bad as you keep trying to imply, you would think the USAF would have expressed more interested in the C-17B. But they haven't, they are very happy with the C-17 as is. Which should tell you something.

Because that speed is relatively high in the C-17

Relative to what? Most airliners can have Vmcg = V1 in certain conditions. Again you try to take standard issues and completely blow them out of proportion.

I think that on the C-17, the VMCG is almost the same as V-2 (take-off speed).

No, Vmcg cannot be higher than V1

I suspect (just a wild guess) that EOCS is an attempt at lowering the C-17s VMCG (and thus reducing its required take-off runway length)

You 'suspect'? Why are you playing coy? Very first link for C-17 vmcg is this

http://ieeexplore.ieee.org/xpl/freeabs_ ... ber=789763

The purpose of EOCS is to improve C-17A takeoff performance, particularly on wet runways, by reducing the minimum control groundspeed (Vmcg)

Which sounds awfully similar to what you just said . . .

I guess it sounds more dramatic to 'suspect' something . . .

It also says they tested it and achieved satisfactory results. It's not clear if it was ever 'released' but the work for it was done.

If it's not in there now it wouldn't take much to add it as it is just a software change.

All this to say that it is not because one demonstrates a 2000 foot take-off on a long runway that it can take off from a 2000 foot runway.

Where has anyone claimed a 2000 ft runway? You keep making strawman arguments to tear down.

[vasu_ray]

Not certain about the EOCS but it may be this:
We've talked about landing distance but there are also take-off issues.
One issue that increases the required take-off runway length of this aircraft is VMCG. It is the minimum speed at which an aircraft can maintain directional control on the ground with an engine out, and with the three others engines at take-off power (when the rudder begins to have enough airflow to help the nose steering counteract the assymetrical thrust). Until that speed is reached, an engine failure means an automatic aborted take-off, otherwise it ends up in the ditch on the side of the failed engine. Because that speed is relatively high in the C-17, one must plan for enough runway to be left in front in case of an abort at VMCG minus 1 Knot.
I think that on the C-17, the VMCG is almost the same as V-2 (take-off speed). So if its powerful enough to take-off in 2000 feet, but that VMCG is only reached at 1900 feet, if an engine failure is reached just before VMCG, the required take off runway will be 1900 feet minus 1 + distance required to stop it from there.
If engine failure occurs at or above VMCG take can be continued if speed is above V2.

I suspect (just a wild guess) that EOCS is an attempt at lowering the C-17s VMCG (and thus reducing its required take-off runway length)

lowering VMCG by using more powerful engines so that more acceleration is achieved at a short distance? In the event of an engine failure during take off we see the following sequence of events
speed < VMCG + engine out -> power down/reverse thrusters + emergency braking -> stop distance

the reverse thrusters of only 2 engines can be engaged when one engine of the 4 is out to make thrust symmetric as the airflow on the rudder is not sufficient under VMCG increasing the stopping distance

regular landing:
speed ~ V2 -> reverse thrusters + braking -> stop distance

so, the stop distance from VMCG vs. regular landing should be close? and VMCG length + landing length = runway length compensating for weather conditions

[Gilles]

There you go again.

1) No, it's to make the C-17 even better, but the USAF has determined that the C-17 is good enough as-is and thus C-17B is dead. There was never a real demand for the C-17B, it was just a Boeing proposal to drum up more sales.

2) If the C-17 was as bad as you keep trying to imply, you would think the USAF would have expressed more interested in the C-17B. But they haven't, they are very happy with the C-17 as is. Which should tell you something.

3) Relative to what? Most airliners can have Vmcg = V1 in certain conditions. Again you try to take standard issues and completely blow them out of proportion.

4) No, Vmcg cannot be higher than V1

5) You 'suspect'? Why are you playing coy? Very first link for C-17 vmcg is this

6) Where has anyone claimed a 2000 ft runway? You keep making strawman arguments to tear down.

1) The C-17 didn't meet its original target specs (the one that said 3000 foot runways) and that claimed the C-17 was going to be a super size tactical aircraft that could do all the C-130 could.

2) Its a great aircraft. But just don't tell me it tap dances.

3) Ever heard the saying "if it aint broke, why fix it" ? Why is Boeing wanting to reduce the VMCG of the C-17 with this gizmo? Because it will reduced the required take-off distance.

4) Since when does "almost" mean "over" ?

5) Did not Google the subject. Most engine-out systems are to help pilots control the aircraft with a failed engine after take-off. This is one that "seems" also there to help the pilots better reject the take-off by reducing VMCG.

6) Where did you read "runway". I wrote a 2000 foot take-off. I saw a light C-17 take off in about 2000 feet of ground roll. Very impressive. But it still requires enough runway to reject the take-off. Which is why it cant do that on a 2000 foot runway was all I claimed.

[GeorgeWelch]

1) The C-17 didn't meet its original target specs (the one that said 3000 foot runways) and that claimed the C-17 was going to be a super size tactical aircraft that could do all the C-130 could.

They never claimed a C-17 could do all the C-130 could, that's absurd.

2) Its a great aircraft. But just don't tell me it tap dances.

They didn't say it tap dances. Maybe the Canadian government did, but sorry, that's not relevant here.

3) Ever heard the saying "if it aint broke, why fix it" ? Why is Boeing wanting to reduce the VMCG of the C-17 with this gizmo? Because it will reduced the required take-off distance.

Cost-benefit analysis?

If you can improve performance for basically free (a software change), great. But if there was a serious problem, they would be looking at doing a major redesign (C-17B). But they're not. Again the USAF is happy with its current performance and sees no need to invest in any significant modifications.

You keep claiming it's a dog, but experience does not bear you out.

4) Since when does "almost" mean "over" ?

Vmcg can never be higher than V1 which can never be higher than Vr which can never be higher than V2. How does that make it 'almost V2'.

I like how you make these veiled barbs at the C-17 ('Because that speed is relatively high in the C-17') with absolutely nothing to back it up. How high is Vmcg? How does it compare to V2? How does that compare to other planes?

6) Where did you read "runway". I wrote a 2000 foot take-off. I saw a light C-17 take off in about 2000 feet of ground roll. Very impressive. But it still requires enough runway to reject the take-off. Which is why it cant do that on a 2000 foot runway was all I claimed.

So let me get this straight. You saw the C-17 conduct an impressive take-off and then used that as a basis to bash it? Astounding.

I think you've let your excessive bitterness for the C-17 cloud your judgment.

No one claimed it could take-off from a 2000' runway, so bashing it for not doing something they never claimed it could do seems odd to say the least.

[krish]

...
I agree with Aditya, the IAF wants C-17 to complement the IL-76 fleet in service, to increase the IAF, airlift capability.

I don't think this is true. Initially, there maybe an overlap as the IL-76s are slowly phased out. But by the end of next decade (2020), IAF's strategic lift fleet will only comprise of C-17s.

There are only 15 IL-76s left in the IAF as of today, and by the time a C-17 deal gets done and inducted into the IAF, the IL-76 will be ready for retirement. The other way to look at is that the planned 10 C-17 will give about equal payload lift capacity as the 20 or so IL-76s IAF had in the past for its strategic lift capability.

hey guys by then there will be MTA with russia which will supliment the il-76 then no need for the old timers let them rest since they have worked long enough

[Gilles]

[
Vmcg can never be higher than V1 which can never be higher than Vr which can never be higher than V2. How does that make it 'almost V2'.

Please do not play stupid. You are far from stupid. Its getting boring for the readers and annoying for me to have to explain and justify every statement I make.

If X aircraft has a VMCG of 120 knots and a VR of 150 knots (lets forget the other factors to make this simple), it needs to roll on the ground until it reaches 150 knots in order to take off. Lets assume that on all four engines it takes 5000 feet of ground roll.
An overpowered aircraft that would lose 1 of its 4 engines (25% of its power) shortly after VMCG could continue the take off roll and perhaps use 5300 feet on 3 engines. By overbosting its 3 remaining engines for a short time, it could quickly accellerate from 120 Knots to 150 knots anyway and the take off penalty would be small. Such an aircraft would have a balanced field length of about 5500 and that would be the minimum take off runway it needed. If this same aircraft rejected take off at 119 knots, the part of the runway it used for rejecting would likely not increase the take off runway required.

If on the other hand this same aircraft had a high VMCG relative to its VR speed, say its take off speed was still 150 knots but its VMCG was 148 knots, if that aircraft experienced a critical engine failure at 145 knots at a moment it had already used 4500 feet of runway, it would have to abort the take off, because although it had enough reserve power to continue the take off, the assymetrical force would be so high that it would be unable to maintain directional control and stay lined up on the runway.
In such a case, its minimm take off runway required would have to be 4500 feet already used up at engine failure, plus a reject distance, say of say 2000 feet, for a total of 6500 feet.

So this second aircraft that had a HIGH VMCG in relation to its VR speed would required a longer take off runway than the first, all other things being equal.

This is why in the planned C-17B, Boeing is attempting to lower the VMCG of the aircraft because in this case, the minimum take off runway required is in fact increased because of its high VMCG in relation to its take-off speed, they are close to each other.

My conclusion about the 2000 feet example, was, that its not because you see a C-17 make a 2000 foot take off roll at an airshow that you must deduct that it can take off from a runway shorter than the minimum runway we discussed earlier in this thread.

I have seen a widebody civilian airliner take off in 3000 feet ground roll. C-17 can do even better.

I wish I didn't have to justify everything thing I write on this thread the way you make me do it. Its really annoying for me and other readers.

And for the Xth time, I never wrote anywhere that this aircraft is no good. Its a fine aircraft, but it is using the sales pitch of its original specs, those that were meant to be in 1989, not those of the aircfraft it turned out to be.

By the way, here is the document that says that originally the C-17 was supposed to land in 3000 feet:

http://archive.gao.gov/t2pbat5/150106.pdf

They once claimed that the C-17, once brought up to 210 on inventory, would allow the C-130 fleet to be considerably downsized since the C-17 was a tactical aircraft as well as a strategic aircraft that could carry oversize equipment directly to the battlefield and land where ever the C-130 could. This was called the "Direct delivery doctrine"
This paper mentions it:
http://www.globalsecurity.org/military/ ... 92/PBW.htm

This paper however, was written AFTER if was revealed that the C-17 could not land on 3000 foot runways and when the direct delivery theory had already begun to take on water. It had since been quietely dropped.

Dont pretend as though none of this ever existed. Its well documented.

[Kersi D]

I could easily argue that with the same $2.5 odd billion dollars, the GOI could easily build an all-weather railway and motorway to both Leh and Tawang that could ship more men and material than the C17 ever could.All this however doesn't mean that the C17 is not a good choice or that there are some nefarious motives behind its acquisition, it merely implies that I hold dear Ronald Regan's favorite Russian phrase " Trust but Verify".

I think you have hit the nail on the head. A very big and potent nail.

Why not spend US$2 billion on a all weather road to Tawang and Thoise and Leh and ....

I am not saying that this super road means that IAF get rid of all its transport. To me it means more bang for the bucks

K

[Kersi D]

Hasn't the IA recently asked for a tender for a 100 "light tanks" for the mountainous regions? Perhaps they want to put 4 tanks apiece in that C 17?

Then The US "light tanks" would require some US ATGMs. Then some US "tank detectors", then some US laser range finders. Then some US AT missile warning system and then some US ...............

This means that the C 17 is a part of large conspiracy !!!!

I think that India buying form US has one HUGE advantage. We are telling Russia not to take us for granted (read not to take us for a ride).

I would not consider US arms peddlers to be saints nor can I say that the Russian peddlers to be the devil himself.

K

[GeorgeWelch]

If X aircraft has a VMCG of 120 knots and a VR of 150 knots blah blah blah

Thank you for reiterating what a high Vmcg means.

Now: Please backup your assertion that the C-17 has a high Vmcg relative to other planes.

My conclusion about the 2000 feet example, was, that its not because you see a C-17 make a 2000 foot take off roll at an airshow that you must deduct that it can take off from a runway shorter than the minimum runway we discussed earlier in this thread.

That's true of any plane.

By the way, here is the document that says that originally the C-17 was supposed to land in 3000 feet:

That's ANCIENT history. No plane meets its designed specs. Even the F-22 has significant shortcomings compared to what was originally hoped for. Anyways this is well documented. There is nothing secret about it. There is no conspiracy to hide the information.

They once claimed that the C-17, once brought up to 210 on inventory, would allow the C-130 fleet to be considerably downsized since the C-17 was a tactical aircraft as well as a strategic aircraft that could carry oversize equipment directly to the battlefield and land where ever the C-130 could. This was called the "Direct delivery doctrine"
This paper mentions it:
http://www.globalsecurity.org/military/ ... 92/PBW.htm

This paper however, was written AFTER if was revealed that the C-17 could not land on 3000 foot runways and when the direct delivery theory had already begun to take on water. It had since been quietely dropped.

It has NOT been dropped. Again you misunderstand the papers you quote. It's tactical ability was being compared to the C-5 and C-141, NOT the C-130. Being more tactical than the C-5 and C-141 means more places the C-17 can go directly and thus less need for the C-130. Notice they did NOT say it would ELIMINATE the need for the C-130.

Every day in Iraq C-17s fly missions directly to bases without transshipping to C-130s. Direct delivery is alive and well


So let me sum up your arguments:

1. It didn't quite meet it's original specs

This is literally 15 year old news that is well documented and not a big deal. Its performance is still very impressive.

2. The fact that some sites still list the original specs is 'proof' that Boeing is trying to hide this failure and confuse any potential buyers.

Any buyer who relies on Google to get the specs of a plane deserves what they get. Boeing has been upfront and truthful about the specs, all anyone has to do is ask.

3. The C-17 can demonstrate an impressive take-off performance, which could potentially confuse some poor military buyer into thinking that it only needs a 2000' runway.

Nevermind that NOWHERE is a 2000' runway capability claimed, no semi-competent acquisition team is going to confuse minimum takeoff-roll with balanced-field length. Claiming this is even a possibility is frankly insulting to their intelligence.

[JTull]

I have not read all the posts here, but just wanted to mention that RAF has just started shipping Merlins to Afganistan loaded onto C-17s. Link

In the aftermath of tsunami, IAF sent it's helicopters over Myanmar for relief operations in A&N islands. Apparently, IAF didn't want to use IL-76 as they were busy carrying other relief supplies. Link

I'm not implying that IL-76s didn't do the job they were tasked; or that if C-17s were there, IAF could have used them to ship helicopters. But IAF would surely have benefitted from more heavy lift capability. C-17s surely would have carried more supplies per flight. Maybe C-17s could have been tasked to carry heavy equipment.

Also, of note is that the airstrip in Port Blair was not immediately available to full length. Another advantage to use C-17s.

[Rahul M]

Also, of note is that the airstrip in Port Blair was not immediately available to full length. Another advantage to use C-17s.

how so ?

[JTull]

Also, of note is that the airstrip in Port Blair was not immediately available to full length. Another advantage to use C-17s.

how so ?

As I recall, the airstrip had developed cracks. Quick googling does not give me any specifc links except this one

This link mentions Carnic runway had 1500ft available while 200ft was submerged.

[Rahul M]

no, I mean do we know for sure that C-17 has better STOL/rough field characteristics than the Il-76 ? could you please provide figures ?
TIA.