The four-engine aircraft is capable of taking off and landing even on makeshift runways, barely 3,500-feet long and 90-feet wide, India will be able to transport soldiers and combat systems to forward areas both on western and eastern fronts much faster.
35+ is not outside 25+NRao wrote:OK. We are making progress. We are down from 30+ to 25+ years.
The problem as I see it is in taking 10,000 feet as one figure and 30,000 as the other figure and say that at 10,000 there is no difference and at 30,000 turbofans do well. It is the space between 10 and 30 that is crucial.indranilroy wrote: after about 30,000 feet though the turbofans have a spread of about 50:50 of thrust coming from the fan and the compressor ... this will not be felt at 10,000 feet where the turboprop at low speeds will still trump the turbofan.
I understand that Turboprops also have slower speed for landing and take off which makes it more tolerant of runway condition. Apart from the fact that turboprop engines are more resistant to ingestion and good for reversing etcindranilroy wrote:no no no ... shivji you have got me wrong on that front ... I am not at all criticizing the the MRTA or it's design ... I am only making a case for a turboprop like the C-27 which has a take of run of just 670 mtrs for the AN-32 replacement ... the MRTA may have been designed keeping high ALGs in mind ... after all choice of engine is not the only thing.
Now coming back to drop in thrust in a turboprop vis-a-vis a turbofan with altitude ... The efficiency of any engine based on a turbine at any altitude is the efficiency of the turbine at that altitude ... the effect on the propellers blades will be the same as on the blades of a turbofan !!! The fact that the turbofan blades are in a duct comes into play with speed and not with altitude ... turbofans are more efficient than the turboprops above 450 mph ... before that the turboprops rule ... after about 30,000 feet though the turbofans have a spread of about 50:50 of thrust coming from the fan and the compressor ... this will not be felt at 10,000 feet where the turboprop at low speeds will still trump the turbofan.
To quote concrete figures C-130J with same payload as the MRTA will have a takeoff run of 900-1000mtrs whereas our MRTA is going to have a run of 1200-1300 mtrs ... this scales up by the same factor as we go higher. So C-130J will still take off or land on shorter runways than the MRTA even at higher altitudes ... Infact given the AE-2100 (the engine that powers the C-130J and the C-27) has excellent performance in hot and high airfields ... the C-27 I heard could do 3G with loads ... this engine has set many altitude and efficiency records.
Reading the report, it seems that they are thinking about an aircraft that will be similar to the proposed RTA that is to be designed by the NAL. Depending on the timeline in question, this may mean, if, a foreign solution is chosen then the IAF may not have the space for a domestic solution.Vipul wrote:IAF proposes to get transport aircraft from private industry.
SNIP.......
Actually India needs around 100-200 aircraft of An-32/Avro category. The license production of C-27 is a reasonable option. MRTA is a very big aircraft, even though its MTOW is stated to be 65tons but looking at its size (equivalent to 737/320s) its MTOW should be in the range of 75-85tons. MRTA's MTOW seems to have been understated to market it as a replacement of An-32. Now IAF has come out with the requirement for a Transport aircraft which will actually be replacement of An-32/Avro but for public consumption citing the replacement of Avrourl=http://economictimes.indiatimes.com/new ... 824933.cms]IAF proposes to get transport aircraft from private industry.[/url]
Reading the report, it seems that they are thinking about an aircraft that will be similar to the proposed RTA that is to be designed by the NAL. Depending on the timeline in question, this may mean, if, a foreign solution is chosen then the IAF may not have the space for a domestic solution.
I don't know how you come to such conclusions! You would have to prove that the top military brass of the Indians, the Brazilians, the Japanese, the Chinese and the numerous operators of C-130J are fools!vic wrote: MRTA is neither here nor there, Russian requirement which has been thrust down Indian throats
Hopefully, the state-industry coupling will make the most of the situation, as India imports uniquely from different continents. An airplane with direct cargo flight from USA to India can avoid 'missing 3-ton LCA parts' kind of situations and aid in speedy all-round development.Pratyush wrote:Reading the report, it seems that they are thinking about an aircraft that will be similar to the proposed RTA that is to be designed by the NAL. Depending on the timeline in question, this may mean, if, a foreign solution is chosen then the IAF may not have the space for a domestic solution.Vipul wrote:IAF proposes to get transport aircraft from private industry.
SNIP.......
I cannot even prove that old lady is not weaving thread on the Moon, so >>? In any case, I have pointed out above that MRTA in not a replacement of An-32 as it is 4 times its size. C-130 & C-27 type/equivalent aircraft will be more suitable for India. The honesty of top brass is legendary.indranilroy wrote:I don't know how you come to such conclusions! You would have to prove that the top military brass of the Indians, the Brazilians, the Japanese, the Chinese and the numerous operators of C-130J are fools!vic wrote: MRTA is neither here nor there, Russian requirement which has been thrust down Indian throats
Not only that, you will not even be prove that the An 32 was the exact and perfect aircraft when it was offered to us or even that a replacement aircraft should exactly replace the An-32 because the An-32 was such an exact and perfect requirement for the IAF that met the IAF's requirements exactly.vic wrote: I cannot even prove that old lady is not weaving thread on the Moon, so >>? In any case, I have pointed out above that MRTA in not a replacement of An-32 as it is 4 times its size. C-130 & C-27 type/equivalent aircraft will be more suitable for India. The honesty of top brass is legendary.
Take-off and approach velocities are a function of weight and wing area. Available power (turbo-prop or turbo-fan) cannot change these numbers. They either have the power to achieve required velocity or not! That's all.indranilroy wrote:Due to the power advantage at low speeds, the the turboprops have much lower approach speeds. Even for our turboprop RTA, the approach speed is 110 kts (take of run of 900-1000 mtrs) whereas that of the turbofan NCA is 125 kts (takeoff run of 1400 mtrs).
Taking a simplistic view (and with the correction that it is lift, rather than the wing area) you are right about the takeoff speed.Shalav wrote:Take-off and approach velocities are a function of weight and wing area. Available power (turbo-prop or turbo-fan) cannot change these numbers. They either have the power to achieve required velocity or not! That's all.indranilroy wrote:Due to the power advantage at low speeds, the the turboprops have much lower approach speeds. Even for our turboprop RTA, the approach speed is 110 kts (take of run of 900-1000 mtrs) whereas that of the turbofan NCA is 125 kts (takeoff run of 1400 mtrs).
So lets take the complicated view. Since you mention lift... here is the lift equationindranilroy wrote:Taking a simplistic view (and with the correction that it is lift, rather than the wing area) you are right about the takeoff speed.
The part highlighted in red is unrelated to your assertion that "higher power = lower approach speeds" which is a completely nonsensical statement.But how you get to the take off speed is what was being discussed.Turboprops can generate more power at standstill and lower velocities and hence accelerates the plane faster to the take off speed.
Again this has nothing to do with higher power = lower landing speed or even higher power = lower takeoff velocity.We are also speaking of planes which would definitely have more than one engine and hence the engines must be wing mounted in this case ... the effective ground speed for takeoff and landing is lowered because of additional lift generated by propwash flowing around the wing.
However, I stand corrected for what I said below:the MRTA may have been designed keeping high ALGs in mind ... after all choice of engine is not the only thing.
2. Isaid ... prop-wash increases lift ... it doesn't ... you made me read more on this ... thank you!Due to the power advantage at low speeds, the the turboprops have much lower approach speeds. Even for our turboprop RTA, the approach speed is 110 kts (take of run of 900-1000 mtrs) whereas that of the turbofan NCA is 125 kts (takeoff run of 1400 mtrs).
It depends on what they want to achieve with IFV , certainly a heavier IFV could/may offer better protection from certain angles at the cost of being heavier and having its impact on its amphibious capability while making it air mobile with certain transport types (IL-76 or C-17 )Rahul M wrote:boss, if you look at other concepts with decent levels of protection they all weigh around the 25 t mark, some are even over 30 t. I expect similar outcome from our IFV competition if they have a decent protection standard.
the hercs are not meant for lifting these since they are SF aircraft but the MRTA, since it is still in design phase should cater for future needs.
indranilroy wrote: The points I made were these.
1. A turboprop accelerates to take-off speed faster than a turbofan ... do you agree/disagree?
2. Turboprops generate more power than turbofans at standstill and at lower velocities ... do you agree/disagree?
3. Below about 450mphs turboprops and turbofans are affected identically by density of air ... do you agree/disagree?
Because of the small number of cycles they put on the airframes. They are used for long haul to support the deployments in Iraq and Afghanistan. If all an aircraft does is 10 hour flights, by the time it has 30,000 hours, its only landed and taken off 3000 times (3000 cycles), which puts very little maintenance strain on the aircraft. If that same aircraft, for lack of a war, did only short training missions or even did touch and goes, it could end its career with 30,000 hours flight time, but with 60,000 cycles, which would have increased its maintenance cost 10 fold. Its like having a car which is only used on highways on cruise control, and another identical car which is always used in low gear, in city traffic, as its used to teach new drivers how to drive.GeorgeWelch wrote:Interesting chart of operational cost per flight hour for different aircraft in the USAF fleet.
http://www.flightglobal.com/blogs/the-d ... ombat.html
Of particular note is that the C-17 actually costs less to operate than the C-130H and only a hair more than the C-130J, even with the difference in fuel burn. I'm not sure how it's possible, but there it is.
These news reports and design of NCA from Aero Show indicate that trurboprop version of RTA has been droppedThe National Civil Aircraft Development Project is set to be launched by January next year, and the total investment for the project is estimated at Rs 8,300 crore.
According to the financial feasibility report for the project, the first phase, or the design phase, is expected to start by January 2012 and would entail an investment of Rs 4,400 crore, which would be spread over a period of three-five years. The second phase, or the production phase, is expected to start within three years of the launch of the design phase, and would require an investment of Rs 3,900 crore.
“Currently, the project is at a pre-design stage and awaits the government’s final approval. NAL has already invested Rs 50 crore and put in place a civil aircraft design bureau, which is expected to develop five prototypes,” said a source involved with the feasibility study. The project involves developing 70-90 sitter ‘short haul aircraft’ to facilitate air transport in Tier-II and Tier-III cities.
The production stage would initially start with a capacity of five aircraft a year, which would be scaled up to 36 aircrafts in five years.
I was actually going to type up the aerodynamic reasons ... but wiki does it better.negi wrote:Well 'Cl' is experimentally derived quantity and is influenced by the wing planform, aspect ratio and wing sweep. The turboprops have low/negligible wing sweeps (except for high altitude and high speed bombers like Tu-95). Turbofans have lower aspect ratio and higher sweep angles when compared to the turboprops . I do not have a formula handy to support my claims but if one would look at the variable geometry wing AC i.e. the flogger/tomcat one would observe that they always take off and land with their wings at lowest sweep setting, to me it means a low sweep angle assists the AC to attain the required 'L' earlier than at higher sweep angles and similarly be able to attain minimum safe approach speed while landing. All in all my understanding is lower sweep angle and a high aspect ratio wing are good for short take off and shorter landing performance.
http://www.grc.nasa.gov/WWW/k-12/airplane/turbprp.html
If you see the thrust equation one would find why the props deliver high thrust at low speeds and if you will draw a garph between thrust and speed ( y and x axis respectively) one will see thrust will decline with increase in speed in the subsonic regime. In case of turbofans above 0.5 M or above the RAM compression will kick in and core will provide increased thrust but until that is reached a turboprop will trump the turbofan in every respect.
When a swept wing travels at high speed, the airflow has little time to react and simply flows over the wing almost straight from front to back. At lower speeds the air does have time to react, and is pushed spanwise by the angled leading edge, towards the wing tip. At the wing root, by the fuselage, this has little noticeable effect, but as one moves towards the wingtip the airflow is pushed spanwise not only by the leading edge, but the spanwise moving air beside it. At the tip the airflow is moving along the wing instead of over it, a problem known as spanwise flow.
The lift from a wing is generated by the airflow over it from front to rear. With increasing span-wise flow the boundary layers on the surface of the wing have longer to travel, and so are thicker and more susceptible to transition to turbulence or flow separation, also the effective aspect ratio of the wing is less and so air "leaks" around the wing tips reducing their effectiveness. The spanwise flow on swept wings produces airflow that moves the stagnation point on the leading edge of any individual wing segment further beneath the leading edge, increasing effective angle of attack of wing segments relative to its neighbouring forward segment. The result is that wing segments farther towards the rear operate at increasingly higher angles of attack promoting early stall of those segments. This promotes tip stall on back swept wings, as the tips are most rearward, while delaying tip stall for forward swept wings, where the tips are forward. With both forward and back swept wings, the rear of the wing will stall first. This creates a nose-up pressure on the aircraft. If this is not corrected by the pilot it causes the plane to pitch up, leading to more of the wing stalling, leading to more pitch up, and so on. This problem came to be known as the Sabre dance in reference to the number of North American F-100 Super Sabres that crashed on landing as a result.
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The swept wing also has several more problems. One is that for any given length of wing, the actual span from tip-to-tip is shorter than the same wing that is not swept. Low speed drag is strongly correlated with the aspect ratio, the span compared to chord, so a swept wing always has more drag at lower speeds. Another concern is the torque applied by the wing to the fuselage, as much of the wing's lift lies behind the point where the wing root connects to the plane. <SNIP>