Roll Speed at Supersonic Airspeeds
As a fighter increases its airspeed when subsonic, its roll will get faster and faster.
But will supersonic flight typically causes a fighter’s roll speed to decrease?
Alfred last edited by
only if the pressure difference on the wings at more than supersonic decrease
Thank you, Alfred.
Regarding roll rate at subsonic airspeeds, is the reason why roll speed keeps increasing and increasing as airspeed increases because:
- faster air moving over the wings
- decrease in AOA
Do both of these contribute to the increase in roll rate?
Stevie last edited by
…all this is highly dependent on which aircraft you’re talking about.
Let’s say a particular fighter aircraft can sustain a 7G turn at 500 KIAS at low altitude. And let’s say the fighter has a very fast roll at 500 KIAS. But, if the pilot was pulling 7Gs, and while pulling 7Gs he pushed the stick all the way to the left for a max roll, wouldn’t his roll be much slower at 500 KIAS because his AOA is higher because he is pulling 7Gs?
So when a fighter is pulling Gs, AOA increases, and thus because of the higher AOA roll rate decreases?
schnidrman last edited by
Look here…It’s for the F-18, but I’m sure the two are similar. I accidentally brought up the wrong link (and I’m feeling lazy ATM) but a similar report is available for the Viper with a Google search.
Look at pg. 92-101
I know it doesn’t specifically answer your question, but I think what you are talking about is kinda out of the performance envelope and not really worth the discussion. That is in no way a knock at you or your question. I’m just saying that if it wasn’t included in the report, it probably means that it is not a typical situation. For instance, lets say I’m cruising @ M 1.05, straight and level and I get a launch warning from somewhere out in front of me. At this point, I am going to slice back or beam which is going to take me out of supersonic flight as soon as I start loading the wing and I probably won’t get past M 1.0 again unless I point the nose straight onto the ground below me, which would probably end badly.
With all that being said, I’ve never really been in a situation in the Viper where I thought I needed more roll authority, so I have to ask…why are you asking? Just curious and not meaning to sound critical.
Of course I may be misunderstanding you completely.
Stevie last edited by
NASA’s HARV was not a “typical” Hornet -
Also keep in mind that the higher you go the slower “Mach” becomes in terms of absolute speed - Mach 1 at SL is far faster than Mach 1 at say, 60K MSL because the speed of sound is slower. And if you’re doing a loaded roll you are by definition at a higher AOA than the previously stated theory that AOA decreases with increasing Mach.
And again, all this varies dependent on the aircraft you’re talking about - airframe design, geometry, control laws (ESPECIALLY for a FBW design), modifications, speed, altitude, Mach, C.G., GWT, thrust, etc. are just some of the variables that come into play. Questions like this are never as simple as we’d like to make them…and it’s far more instructive if one contains the discussion to one airplane. Like an F-16, maybe?
BTW, the X-31 mentioned in this paper happened to crash during a flight test (and I forget if the pilot was lost in that indecent or not, but one could look that up), and maybe that’s why MBB hadn’t released/published their data at the time this paper was written? The chart I’d like to have seen isn’t contained in this paper…for the very reasons stated in the paper.