Air Force Question Thread

[anoopsaxena76]

PhD in Aerodynamics and my son is doing his PhD in Astrophysics.
..............
So you can ask me anything regardless of what you think is a stupid question, is actually not stupid. knowledge is knowledge no matter what others say. There are a very few people who have really seen a Fighter let alone fly one, You might be very educated but sitting a flying is a totally separate thing and having a couple of boogies under your belt makes hell of a difference.
So ask anything except weapons I will not go into details unless PAF has openly told everyone. .....

Hello Mr. Murad, just wanted to thank you. Have read many posts and your views / replies and have to tell you, it is a pleasure to read your insights. We may have a history of two wars behind us as citizens of two different countries but my objectivity allows me to respect men in uniform irrespective of the country and so taking this opportunity to share my thoughts with you. This particular thread has given good insights and hoping to read more on aerodynamics etc. I do have a question though, and if I may narrate an incident before that.

My brother-in-law a retired commodore from the IN, did his Engineering from IIT (a highly reputed institute in India for the benefit of those who may not know) and then his masters from UK sponsored by the IN. You may have heard of the ATV project (the nuclear submarine project in India) which really is not going anywhere frankly and he was part of the team that was posted in Russia to understand and absorb the technology. He narrated this incident to me. After a few classes of training, the Indian Engineers demanded that they be handed over the notes which they can read in leisure time thereby expediting the entire learning process instead of being taught like in a class room. Initially Russian instructor hesitated but upon persistence he gave the notes away. And my brother-in-law tells me that the science in those notes was really so advanced that the team could not make much of it.

So my question is, what is the technology gap between US/ Russia and Pakistan/India, of course only about things that you can disclose. I realise it is a very open ended question in terms of "technological gap in which field" but I leave it to you to address it. I hope you do not mind.

Thanks and kind regards,
Anoop.

 

[Tang0]

Engine does care. Aircrafts have different ranges at different altitudes, why? because the engine does care. Thats why the designers optimise an engine for a given altitude.

The engines of Tornado are optimised for low-level flight and their performance at medium level is not impressive. Air superiority fighter engines are designed for medium level altitudes and they burn more fuel at low altitudes, reducing their range at low level.

At higher altitudes, air density is lower, which can cause a reduction in thrust, if engine is not optimised for this altitude. A reduction in thrust for a given fuel reduces the specific fuel consumption (sfc).

The issue essentially amounts to how fast you want to get somewhere. For lift to be equal to weight(IE to "fly"), if we increase velocity, to stay in level flight, we need to decrease the air density. Otherwise, we climb, which has the side effect of decreasing the air density anyway.

Hard for me to digest. Aircrafts regularly accelerate to supersonic speed while remaining at level flight. Increasing velocity does not mean that we must climb (to reduce air density).

Note that I say "Stay in steady Level Flight". That means without changing your angle of attack, which changes lift generation, and the direction of your lift vector. You can lower your nose and stay at the same altitude, but you will have decreased your fuel efficiency in order to do so. This is one of the many reasons that dog fighting is incredibly costly from a fuel standpoint.

About the engines: You are correct, but the simplifying assumption is not all to terrible for a "Hand Wavy" discussion. At least, that is what my professors said when I was an undergrad.

All of that said, I would love to talk tech with an actual Ph.D. with fighter experience. I am a recent BA recipient in aerospace, and I freely admit the depths of my ignorance when it comes to the intricacies of flight stability and dynamics.

 

[blain2]

I was wondering if PAF uses Maverick missile for air to ground attacks basically used to take out tanks and other land based military hardware, can any one with the proper knowledge please answer my question?

Yes AGM-65s are in the PAF inventory for use on the F-16s. AS-30s are used by the Mirages in a similar role.

 

[MastanKhan]

Jets have a similar fuel efficiency for a given thrust all throughout their operational altitudes, so the engine does not really care.

Engine does care. Aircrafts have different ranges at different altitudes, why? because the engine does care. Thats why the designers optimise an engine for a given altitude.

The engines of Tornado are optimised for low-level flight and their performance at medium level is not impressive. Air superiority fighter engines are designed for medium level altitudes and they burn more fuel at low altitudes, reducing their range at low level.

At higher altitudes, air density is lower, which can cause a reduction in thrust, if engine is not optimised for this altitude. A reduction in thrust for a given fuel reduces the specific fuel consumption (sfc).

The issue essentially amounts to how fast you want to get somewhere. For lift to be equal to weight(IE to "fly"), if we increase velocity, to stay in level flight, we need to decrease the air density. Otherwise, we climb, which has the side effect of decreasing the air density anyway.

Hard for me to digest. Aircrafts regularly accelerate to supersonic speed while remaining at level flight. Increasing velocity does not mean that we must climb (to reduce air density).

Hi,

Could not resist---you got me out of my break / vacation---we need to remember that the higher we climb---the lesser the amount of oxygen is available to burn---so that creates a problem---which is the starvation of combustion because of lack of oxygen fuel---

oh guess what---can't do a cobra at high altitude either---any immediate change in direction of an aircraft at high altitude would disrupt the air flow to the engine---resulting in a possible 'compressor bump / stall' ( am I right MuradK )

Another examples is in automobiles----they are tuned differently to be driven at sea level---unless they have the modern fuel injection systems which automatically adjust the amount of fuel and air and ignition timing for higher altitudes. But then still there are limitations---all the compensations can only do so much---lack of oxygen would just starve the engine and reduce the power.

 

[Tang0]

Do we dare open this can of worms...?

The problem is what precisely you are talking about. If you know anything about compressible supersonic flow, you know that things behave...oddly after the speed of sound. So are we talking about M <1 or > 1? Are we talking about high bypass turbofans, or turbojets? There are big complicated equations relating air density, velocity, temperature, specific heat capacity, and half a dozen other things, to specific thrust, and they are slightly diffrent for every engine.

The reason I did my hand-wavy simplification is that although net thrust decreases with altitude, you have to fly at higher velocities at higher altitudes to stay aloft in any case. And the effects for velocity and density are both "Close to" linear, so they "Mostly" cancel each other out. Of course, I was making all types of simplifications in the first place, assuming all we really cared about was getting the farthest on a tank of gas, and ignoring things like weather and time constraints. Along with changes in AOA, the need to turn....

Any mathematically rigorous analysis as you can see is going to explode fairly quickly. There are engineers who spend many months of analysis picking specific engines for specific airframes with specific missions, and, they often get it wrong.

Should we create a separate thread for "Technical Discussions" where all us rotor heads can hash this type of stuff out?

 

[HAIDER]

I have seen lots of debate about Delta and non delta wing aircraft. Historically non delta wings like F16,F14,F15,F18 has highest kill ratio in the world. But present day everyone has launched delta wings, Rafale,Euro,LCA,J10,Mirage,etc. Some of critics support the point of having less Delta wings in Pakistan air force, because they have very limited role. Mainly navel warfare. Are we following the concept of successful use of Argentina's Mirage during falkland war, sinking HMS Shaff..
Why ?...


Second part of my Question to Sir Murad or anyone, did PAF learn the best use of Mirage after Falkland war or PAF already had the concept, before Argentina.
...But Sir Brits gives the argument HMS Shaf was not in function mode and some Brits say,Shaff radar was not capable of catching low flying in comings)

 

[MaXimMaRz]

I have seen lots of debate about Delta and non delta wing aircraft. Historically non delta wings like F16,F14,F15,F18 has highest kill ratio in the world. But present day everyone has launched delta wings, Rafale,Euro,LCA,J10,Mirage,etc. Some of critics support the point of having less Delta wings in Pakistan air force, because they have very limited role. Mainly navel warfare. Are we following the concept of successful use of Argentina's Mirage during falkland war, sinking HMS Shaff..
Why ?...


Second part of my Question to Sir Murad or anyone, did PAF learn the best use of Mirage after Falkland war or PAF already had the concept, before Argentina.
...But Sir Brits gives the argument HMS Shaf was not in function mode and some Brits say,Shaff radar was not capable of catching low flying in comings)

1. Delta wing Aircraft are basically designed for High payload and there for are high speed Aircraft cuz the stall speed is a bit higher.

2. delta wings produces Induced drag ( How ever Canards and Thrust vectoring can catter for that i.e in terms of performance only)

3. The old delta wing Aircraft, i mean the ones not having modren avionic may not perform as good as a non-delta in a close combat ( the reason is induced drag)

4. PAF is very much capable of utilizing its Delta wings ( Mirages are the supreme example of slash and dash tactics)

5. There role is not limited to just a load dumping platform. With a Good AI or ground control , these high speed platforms play hell in close combats.

6. Every structure has its advantages and disadvantages, and we posess a good ratio and a good combo of such structures. So no worries in this aspect

 

[Muradk]

I have seen lots of debate about Delta and non delta wing aircraft. Historically non delta wings like F16,F14,F15,F18 has highest kill ratio in the world. But present day everyone has launched delta wings, Rafale,Euro,LCA,J10,Mirage,etc. Some of critics support the point of having less Delta wings in Pakistan air force, because they have very limited role. Mainly navel warfare. Are we following the concept of successful use of Argentina's Mirage during falkland war, sinking HMS Shaff..
Why ?...


Second part of my Question to Sir Murad or anyone, did PAF learn the best use of Mirage after Falkland war or PAF already had the concept, before Argentina.
...But Sir Brits gives the argument HMS Shaf was not in function mode and some Brits say,Shaff radar was not capable of catching low flying in comings)

Yes we did learn from FalkL War that man behind the machine does matter, Our cadets were better pilots than them, While doing a course in
uk they showed us all the Air -to- Air kill. Most of the kills were not above 2gs and most were flying straight, You never flying straight in a Air War.
We at PAF have been flying Mirages 12 years before FalkL , We established UAE airforce, I flew Mirages from France to UAE 3 times.
During my command of 9 Sqd I had 1 vs 1 Dogfight with Hakilullah Ex COAS than the base commander during the dogfight I pulled 7.6gs one of the most difficult landings in my career the wings got screwed up. That Mirage was grounded for 6 months a replaced by another.

 

[MastanKhan]

Haider,

It is not only the british that use the excuse that HMS SHAF was not ready for what happened to it or it was not capable---

Doesn't this statement sound familiar on our own home turf---you fight battles with what you have purchased and trained on five years ago---when you go to war, you put your best foot forward----

Any old timer remember the first wrestling match between AKRAM PEHLWAN & ANTONIO INOKI and the bull-s-h-i-t that Akram Pehalwan started with before ther fight and the crying game he played after losing the fight0--- " us nay meri ankh mein ungli mari " " fir us nay mera bazoo tor dia " ( he poked my eye ) here is what Aki pehalwan stated shamwelessly---english translation----first he poked me in the eye---then he broke my arm. The only problem with that fight was that Akram was not prepared to fight Inoki---Akram was already too old and had not fought too many matches---oto Inoki was younger stronger and andf very tactful----people can translate it what they feel is fit---and deduct their own conclusions.

And indeed, if the RAF was facing PAF instead of argentinian AF, the royal navy fleet would have been history alongwithg the carrier battle group.

 

[HAIDER]

So, Delta wing can be good bomber, cuz it has better load carrying , but not good interceptor ??????...If mirage on operation then it need wings ??either F7 or F16?.atleast one or two..

Sir , Brit still say, During the Falkland war they had non radar for low flying incoming. And same wording when in 199 Pak mirage breakin American fleet during exercise, Fleet was not equipped with any radar for low flying....But i can't take this it was 1995 and Falkland war was 80s era

 

[MastanKhan]

So, Delta wing can be good bomber, cuz it has better load carrying , but not good interceptor ??????...If mirage on operation then it need wings ??either F7 or F16?.atleast one or two..

Sir , Brit still say, During the Falkland war they had non radar for low flying incoming. And same wording when in 199 Pak mirage breakin American fleet during exercise, Fleet was not equipped with any radar for low flying....But i can't take this it was 1995 and Falkland war was 80s era

Hi,

You are absolutely correct---radar or no radar---when I enter the field of war---what am I going to say to Sqdrn Ldr Jaswant Singh---oye sardara---I don't have BVR missiles yet---can we fight this war another day---so that we are evenly matched.

Here is what the brits and the yanks are telling---we need to undrstand their language---what they are saying is that even though we have radars---but there is a certain anamoly that happens that the low flying birds can fly through our protective canopy without being seen. Now it is upto the enemy to manipulate that situation to his advantage.

So let me go back---what the brits and yanks were saying was not what they meant---exactly for that reason---you have to put yourself in your ewnemies shoes and think like him----what is your adversary trying to say when he makes a statement---.

That radar things was a can of big big worms for the brits and the yanks----they were trying to hide it from the russians and others how the security of their carrier battle group could be breached.

The delta wing is the pride of the french air force as well as the paf alongwith australians---the israeli air force---the israelis would have never procured mirages---if the m3/5 was not a great fighter interceptor in its class.

 

[Tang0]

Alot of the success of delta wings can be attributed to the fact that they are relatively cheaper to create and maintain compared to say the cropped delta wing of the f-16 for example.
Because of the way shock waves form, they also perform better at high altitudes in supersonic flight. See Boeing: History -- Products -- North American Aviation XB-70A Valkyrie Research Aircraft

Disadvantages include high induced drag during, and the fact that it has a fairly low angle of attack before you stall compared to other military aircraft designs. The eurofighter typhoon does some very clever things with its forward canards and good avionics to help alleviate this problem. This adds cost, which is contrary to one of the reason the delta wing was popular in the first place.

Long story short, if you need supersonic performance on a budget, and are willing to sacrifice some maneuverability to get it, the delta wing is the way to go.

 

[Zarbe Momin]

I have a question!
F-16 block 60 has overblown (swollen) part on both sides behind the cockpit where wings attach to main frame of aircraft, adjacent to wings and airframe. It is also now visible on J-10B airframe. What is this. If this is for fuel storage why we dont design new block of JF-17 like this.

 

[niaz]

I have had many discussions with the aircraft designers at the Farnborough Air shows on the subject of delta versus swept wings. I would therefore like to add a few additional points to the very informative reply of Hon MAximMarz.

Delta wing is structurally stronger than swept wing of an equivalent weight; therefore it is preferred shape for supersonic aircrafts. Even civilian supersonic aircrafts such as Concord and the ill fated Boing SST were of delta wing design. However, due to high induced drag at low speeds, delta winged aircraft loses speed rapidly specially while turning. Up to transonic speeds and at low altitudes; a swept wing aircraft will be more maneuverable and has a definite edge. Some aircrafts such as F-111 and F-14 were designed with folding wings, to take advantage of both the shapes in a single aircraft.

The loss of lift at low speeds can be overcome to some extent by the addition of a small wing at the forward section of the fuselage known as canard. This also acts as a controller of airflow similar to the elevators.

Advantages of the delta are evident from the fact that nearly all modern high performance aircrafts are of delta wing and those that are not, such F-18; utilize delta in the form extensive leading root edge extension. Sukhoi Mk1 on the other hand has large forward canard in combination with the swept wing.

 

[araz]

Haider,

It is not only the british that use the excuse that HMS SHAF was not ready for what happened to it or it was not capable---

Doesn't this statement sound familiar on our own home turf---you fight battles with what you have purchased and trained on five years ago---when you go to war, you put your best foot forward----

Any old timer remember the first wrestling match between AKRAM PEHLWAN & ANTONIO INOKI and the bull-s-h-i-t that Akram Pehalwan started with before ther fight and the crying game he played after losing the fight0--- " us nay meri ankh mein ungli mari " " fir us nay mera bazoo tor dia " ( he poked my eye ) here is what Aki pehalwan stated shamwelessly---english translation----first he poked me in the eye---then he broke my arm. The only problem with that fight was that Akram was not prepared to fight Inoki---Akram was already too old and had not fought too many matches---oto Inoki was younger stronger and andf very tactful----people can translate it what they feel is fit---and deduct their own conclusions.

And indeed, if the RAF was facing PAF instead of argentinian AF, the royal navy fleet would have been history alongwithg the carrier battle group.

mastan Khan
You have reminded me of the good old days. Man what a pallavva.The only addition to your post that I would put forwards, is that, Uk at that time was also a nuclear power, and had we fought them and decimated their fleet, they would just have nuked us. Thatcher threatened to do so to Argentina, if France did not give UK the source codes for Excorcet missiles and france duly obliged.
WaSalam
Araz