Do modern fighter pilot still do it that way?
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Do modern fighter pilot still do it that way?
I've watched couple of footage about WW2 era fighters, and noticed a quite interesting phenomena, when those WW2 fighters try to do a diving attack, a lot of them do it up-side-down, or do it sideways. They usually roll left or roll right first, then rush toward the ground. I guess it's probably because they just had meal or something, so their tummy kinda refuse to take the negative Gs. While during peace time, you have abundant time to take the rest after dinner, so you don't have to do it sideways or upside down because your tummy is relatively empty.
Am I making the right judgement here? Do modern day pilots still pull the same trick when ... let's say on a CAS run?
Am I making the right judgement here? Do modern day pilots still pull the same trick when ... let's say on a CAS run?
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I believe that its now time to put some myths to bed. The real reason for this tendency to make positive G dives and turns is that fighter pilots loathe spilling their drinks. It is not widely recognised that fighter cockpits, since the early 1930's, have included a automatically deploying drinks holder. Indeed. the original inventors of the device, Chalmondely-Warner Aerospace Ltd. of Godalming, Surrey - have fought several court battles with Samsung, LG, Panasonic, Sony and other electronics giants who, they alleged, used the patented mechanism in their new fangled CD / DVD drives.
If you doubt the veracity of my submission, I offer in evidence the progression, starting in the early 1970s, to Western Air Forces having all graduate and commissioned fighter aircrew. This was, despite a great deal of convoluted stories of an intentionally misleading nature, about the intellectual demands and moral responsibility of the calling of flying sodding great big fighters.
The real reason is that Sgt pilots drink pints of beer. These are heavy and can easily overstress the drinks holder. Officers. on the other hand, are, in the main, sexually progressive individuals who are good colour coordinators and favour sherry or gin and tonic. A gin and tonic, at 6 G, imposes relatively little stress on the drinks holder.
Or it could just be that it is the easiest way to do it.
If you doubt the veracity of my submission, I offer in evidence the progression, starting in the early 1970s, to Western Air Forces having all graduate and commissioned fighter aircrew. This was, despite a great deal of convoluted stories of an intentionally misleading nature, about the intellectual demands and moral responsibility of the calling of flying sodding great big fighters.
The real reason is that Sgt pilots drink pints of beer. These are heavy and can easily overstress the drinks holder. Officers. on the other hand, are, in the main, sexually progressive individuals who are good colour coordinators and favour sherry or gin and tonic. A gin and tonic, at 6 G, imposes relatively little stress on the drinks holder.
Or it could just be that it is the easiest way to do it.
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-ve G slower than +ve G?
Yes basically a positive G turn is quicker/tighter/faster/whatever than a negative G one. If that is what you are asking.
Stik
a humble ex GD/N aerobatic display pilot
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It is worth noting that the Merlin engine in the Spits and Hurries was starved of fuel with negative G applied.
There is no doubt that that the dive angle required could be more rapidly established with a straight push provided that it was within the negative G limit which is usually much lower than the positive limit; however, if a steep dive angle was required, rolling and pulling might be the only way to keep sight of the target - particularly in an aircraft with a long nose and maybe a big prop in the way.
There is no doubt that that the dive angle required could be more rapidly established with a straight push provided that it was within the negative G limit which is usually much lower than the positive limit; however, if a steep dive angle was required, rolling and pulling might be the only way to keep sight of the target - particularly in an aircraft with a long nose and maybe a big prop in the way.
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stiknruda: An Engineer Writes:
If you're an aerobatic pilot, you'll know that things like the Extra & "Special" Pitts Specials often have more symmetric G limits (Like -7/+9) rather than those of combat aircraft (F-16 - -3/+9G) - others around here will know these numbers more accurately. I imagine that the 2nd poster was referring to that.
The why, briefly, 3 main reasons:
Human physiology: It's easier for blood vessels in the eye & brain to cope with reduced blood pressure than it is to deal with increases (a little like submarines vs spacecraft). Aerobatic aircraft normally 'spike' up to their limits & come straight back down again- which biology copes with. Combat aircraft get up to a G level and are expected to sustain it. To do so at -ve G for extended durations (like 3+ seconds) could lead to local tearing of the blood vessels - I believe pilots call this 'Red-out'. In principle, they should also experience minor headaches for a day or two after red-out incidents - although that's pretty much my logical guess rather than documented {edit - shock, Google suggests that it does this plus increases the risk of rather more serious stuff!}. In contrast, grey-out/black-out is purely about cell oxygenation & as long as oxygen deprivation lasts less than 4 minutes, there will be no effects after a few seconds of restored blood flow.
Structures: Combat aircraft tend to be bigger than aerobatic aircraft, so the moments (force x distance) are a lot higher - like a Tonka truck survives a fall much better than a full scale truck. You also tend to find that the loads from weapons & heavy landings act in useful directions for +ve G, so +ve G tolerance is easier to build in.
Stall aerodynamics: Us lot (aero engineers) normally find it better to use a wing with a good L/D ratio for efficient cruise. But they'll normally stall about 20 degrees or less incidence - and they will do so symmetrically (the same angle whether it's nose up or nose down). Most wings are cambered to add a few degrees effective incidence so that the fuselage is flatter in cruise flight. When we try to get up higher lift levels - but only transiently - it's easier to add things like flaps, vortex strakes, Leading Edge Extensions and non-linear twist that favour one incidence limit or the other. We normally tweak it so that all of these aid the +G by extending either the lift limit (CL max) or the controllability of the aircraft - or both.
Well... that and pilots are very demanding of their drinks holders...
If you're an aerobatic pilot, you'll know that things like the Extra & "Special" Pitts Specials often have more symmetric G limits (Like -7/+9) rather than those of combat aircraft (F-16 - -3/+9G) - others around here will know these numbers more accurately. I imagine that the 2nd poster was referring to that.
The why, briefly, 3 main reasons:
Human physiology: It's easier for blood vessels in the eye & brain to cope with reduced blood pressure than it is to deal with increases (a little like submarines vs spacecraft). Aerobatic aircraft normally 'spike' up to their limits & come straight back down again- which biology copes with. Combat aircraft get up to a G level and are expected to sustain it. To do so at -ve G for extended durations (like 3+ seconds) could lead to local tearing of the blood vessels - I believe pilots call this 'Red-out'. In principle, they should also experience minor headaches for a day or two after red-out incidents - although that's pretty much my logical guess rather than documented {edit - shock, Google suggests that it does this plus increases the risk of rather more serious stuff!}. In contrast, grey-out/black-out is purely about cell oxygenation & as long as oxygen deprivation lasts less than 4 minutes, there will be no effects after a few seconds of restored blood flow.
Structures: Combat aircraft tend to be bigger than aerobatic aircraft, so the moments (force x distance) are a lot higher - like a Tonka truck survives a fall much better than a full scale truck. You also tend to find that the loads from weapons & heavy landings act in useful directions for +ve G, so +ve G tolerance is easier to build in.
Stall aerodynamics: Us lot (aero engineers) normally find it better to use a wing with a good L/D ratio for efficient cruise. But they'll normally stall about 20 degrees or less incidence - and they will do so symmetrically (the same angle whether it's nose up or nose down). Most wings are cambered to add a few degrees effective incidence so that the fuselage is flatter in cruise flight. When we try to get up higher lift levels - but only transiently - it's easier to add things like flaps, vortex strakes, Leading Edge Extensions and non-linear twist that favour one incidence limit or the other. We normally tweak it so that all of these aid the +G by extending either the lift limit (CL max) or the controllability of the aircraft - or both.
Well... that and pilots are very demanding of their drinks holders...
Last edited by RugGun; 7th Mar 2010 at 15:27.
""It is worth noting that the Merlin engine in the Spits and Hurries was starved of fuel with negative G applied. " soddim
Until, of course Miss Shilling Gave the RAF her orifice.
Until, of course Miss Shilling Gave the RAF her orifice.
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You'll find that with most WW2 piston aircraft the view forward\below and to the immediate left and right below was inherrantly poor due to the position of the cockpit in relation to the wings and the engine being stuck right out front. That is why most of the postioning of the aircraft was way off to one side of the target or as one ground attack Spitfire pilot told us, "you flew over the target at a reasonably height so they didnt think you were going for them, then you rolled over and pulled back on the stick and went down to come at them from 'behind'. The enemy often thought you'd moved on so they didnt get their flack going up at you quite so quickly, even a few seconds made a lot of difference to you. You accelerated very quickly, lined up, fired\dropped your bombs and left the area at very low level going like stink"
Ive always found Pos G slightly more comfortable than Neg g but Im no super dooper hero Jet jockey.
The later marks of Spitfires did not suffer from fuel starvation problems.
Ive always found Pos G slightly more comfortable than Neg g but Im no super dooper hero Jet jockey.
The later marks of Spitfires did not suffer from fuel starvation problems.
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When you roll up-side-down for a dive attack you also have the added bonus of being able to maintain tally on your intended target.
Today with JHMCS you can always see the diamond whenever you look around but the lead in features necessary to execute a flawless groundattack are missing when you look at your groin throughout a bunt over maneuver
Another point is also that todays payloads increases the stress on the wings and they don't take to well when they are exposed to negative Gz compared to positive. Example are GBUs where an F-16 has +5.5 but only -1.0 reagardless of fuel.
And finally an F-16 can only do negative G maneuvers for up to 30 seconds and 0G maneuvers for 10 seconds due to oil limations.
Today with JHMCS you can always see the diamond whenever you look around but the lead in features necessary to execute a flawless groundattack are missing when you look at your groin throughout a bunt over maneuver
Another point is also that todays payloads increases the stress on the wings and they don't take to well when they are exposed to negative Gz compared to positive. Example are GBUs where an F-16 has +5.5 but only -1.0 reagardless of fuel.
And finally an F-16 can only do negative G maneuvers for up to 30 seconds and 0G maneuvers for 10 seconds due to oil limations.
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You're all missing the obvious...
... It's done with +ve 'g' because when yer man with the stick pulls too hard, he will see his wings detaching from his steed and flapping past him, giving him the not too subtle cue to 'step over the side.' If he applied -ve 'g', he would be deprived of this basic, yet unmistakeable cue. 
