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franc
23rd October 2010, 04:43
Here is a link told me that Hornet are able to achive 720 pds for roll-rate. Is this true with and source?
What about MiG-29?

Scorpion82
23rd October 2010, 10:51
That would mean 2 rolls within a second, highly unlikely. The SH has a roll rate of 225°/sec. This was stated in a test flight article which was posted here as well. MiG-29 should be around the same.

Batman
23rd October 2010, 10:56
Mirage III and A-4 were pretty quick - at least 360/sec, if not slightly more.

Schorsch
23rd October 2010, 19:32
I think the F-16 makes 360°/sec.
In most modern jets the max roll rate is limited by flight control system.

Best roll rate should be displayed by aircraft like the F-104, MiG-23, Mirage 2000 and alike.

franc
26th October 2010, 03:36
I have no idea why the link address was lost, here is added as follow
http://www.airliners.net/aviation-forums/military/read.main/97791/

I remember hearing that for instance (at least the early) the F/A-18's could achieve instantaneous roll-rates of approximately 720-degrees per-second. From what I remember, the A-4 also had roll-rates of about 720-degrees per-second (though I'm not sure if that's a peak roll-rate, like not just the roll rate you'd reach when you have the stick all the way to one side immediately -- which is an instantaneous roll-rate -- but if you held the stick to one side for a little bit and allowed the roll-rate to build up) as well.

The words pretty clear show that roll-rate is degree of per-second with no explaination of how many rolls sustained within, therefore, if there is two rolls, it is shouldn't be in per-second, per-second means merely one second isn't it?
No body go to there to correct it?

Scorpion82
26th October 2010, 12:04
How serious can we take that poster? Is he a pilot has he flown said aircraft or does he have any other references? Doesn't look like that.

alfakilo
26th October 2010, 13:19
How serious can we take that poster? Is he a pilot has he flown said aircraft or does he have any other references? Doesn't look like that.

Good question.

High roll rates are very disorienting. Depending on aircraft type, there is the danger of loss of control due to inertia coupling (airplane goes sideways) or exceeding the aircraft structural limits (tail comes off). For the F-104, for example, the max rate of roll as stated in the flight manual is 360 degrees per second. Similarly, I remember the T-38 as having a similar restriction.

From an operational perspective, I can't think of a reason or maneuver that would require roll rates of 700 dps or more...for one thing, I doubt that the typical pilot would be able to effectively control such a roll rate (meaning the ability to use that roll rate to attain a desired bank angle)...and I suspect the angular momentum that such a rate would result in would make such precise control highly unlikely.

But most of all, I'm concerned about the type of helmet the pilot would be wearing...add that weight to the typical weight of a human head and what we end up with is a lot of pulled neck muscles and concussions resulting from smacking the canopy.

Rookh
26th October 2010, 13:40
Reminds me of the famous Russian quote about the Mig-29; 'The pilot will break before the aircraft does'.

Perhaps instantaneous roll rates are more appropriate as a measure for aircraft performance in combat scenarios?

alfakilo
26th October 2010, 22:00
Perhaps instantaneous roll rates are more appropriate as a measure for aircraft performance in combat scenarios?

I doubt it. Given the amount of time that an aircraft spends in a max effort roll, the distinction, if any, between sustained and instantaneous is irrelevant.

luca
27th October 2010, 08:23
Maybe, roll rate is more important in turn (for turn reversals) where roll at lift counts??
Whether fighter, under these conditions can roll at 50 deg per sec (dps) or 5 dps or roll command will produce roll in opposite direction or it will even cause spin entry ???
There are all these Aileron Alone Departure and other parameters and derivatives ...

Batman
27th October 2010, 08:36
Instantaneous and sustained turn rates and G are more important in close combat than roll rates.

haavarla
27th October 2010, 08:54
Agreed.
The Flanker do not have the same response in roll break as other smaller fighters have.
But the Flanker advantage of the Instantaneous and sustained turn rates and remain in that turn seeing whose energy bleed out first..
Anything else would be crazy..

luca
27th October 2010, 11:46
And what are the Su-27's inst.&sust. turn rates, official ?

Flanker roll rate at 1g - low alpha is one thing and at high g/hi alpha another.
Size of fighter is not so dis/advantageous but roll surfaces area or roll control moment to roll inertia ratio. Aircraft can have full span ailerons like these small aerobatic planes, but wing structure has to be heavier for the same max q speed.

alfakilo
27th October 2010, 13:10
Maybe, roll rate is more important in turn (for turn reversals) where roll at lift counts??
Whether fighter, under these conditions can roll at 50 deg per sec (dps) or 5 dps or roll command will produce roll in opposite direction or it will even cause spin entry ???
There are all these Aileron Alone Departure and other parameters and derivatives ...

In general, rolling and turning are two different things. A pilot uses his roll control to establish a desired bank angle...and then he uses back pressure (elevator) to produce the lift that actually turns the airplane.

There are exceptions when the pilot wants both a roll and a pitching force at the same time. The intent is to have the lift vector changing its direction while the nose is pitching up. For example, the High G Roll. But for most applications, the pilot will roll first, then pull.

As for departures and spins, some fighters (the F-4, for example) had a problem with adverse yaw when making aileron inputs at high angle of attack (AOA). In this situation, the aileron on the wing going up produced enough drag to pull that wing "back" as the jet rolled...the result was a tendency to roll in one direction while yawing in the opposite direction. If this condition was aggrevated enough, the outcome was a 'departure' (uncontrolled pitching, yawing, and rolling) that could end up in a spin if not corrected.

The answer to this was to relax back pressure since the thing causing the problem is the AOA...without the high AOA the aileron input wouldn't create a problem. Back in those days, the saying was "Unload For Control"...meaning, when encountering an incipient departure, 'unload' (move the stick forward) to reduce the AOA and thereby reduce the tendency to create adverse yaw.

Regarding reversals, how they are flown depends on the situation. Reversals can be characterized as 'slow' or 'fast'. In a slow reversal, the pilot uses rudder and elevator to generate an angle of attack and pitching moment that produces the intended flight path. A fast reversal is a 'roll and pull' maneuver where the pilots rolls to the desired attitude and then applies back pressure to rotate the nose. Reversals are common defensive responses when an attacker overshoots...slow overshoot, slow reversal...fast overshoot, fast reversal.


Instantaneous and sustained turn rates and G are more important in close combat than roll rates.

We have to be careful when we make generalizations about air combat maneuvering. This subject is extremely conditional on a number of parameters...speed, altitude, weight, configuration, and desired outcome.

Depending on the desired outcome, it may be that roll rate may be more important that turn rate or radius...for example, in WW2, poorer turning but better rolling US fighters such as the Wildcat could use their rolling capability to break away from a pursuing Zero. In a slow scissors. lift vector orientation is all important...the ability to generate a higher roll rate than your opponent means that you get to point behind him quicker than he can point behind you. The outcome is that he is pushed out in front and you get to gun his brains out.

haavarla
27th October 2010, 16:20
luca;1656231]And what are the Su-27's inst.&sust. turn rates, official ?

I wouldn't know, there is a small different on the different Flanker version.
With and without Carnards, TVC, singel vs two crew stations, engines output thrust..etc etc.
The ultimate Flanker would be the Su-35S.. which of course we have to wait and see any official data.


Flanker roll rate at 1g - low alpha is one thing and at high g/hi alpha another.
Size of fighter is not so dis/advantageous but roll surfaces area or roll control moment to roll inertia ratio. Aircraft can have full span ailerons like these small aerobatic planes, but wing structure has to be heavier for the same max q speed.

Yes, but what i meant was that the Euro-Carnards/gripen and Mirages have better response time rolling vs a Flanker, not a whole lot but there is a difference.
The first 90 deg roll-over is the important one, not 360 or 720 deg;)

Moggy C
27th October 2010, 16:29
Best roll rate should be displayed by aircraft like the F-104, MiG-23, Mirage 2000 and alike.

Outside display aircraft of course.

Extra 300 rolls at 360-420 degrees per second.

Moggy

BlauerMax
27th October 2010, 17:22
The Mitsubishi F-2 appears to have a very high roll rate. Its very snappy. Anyone know its rollrate?

Schorsch
29th October 2010, 11:19
IAs for departures and spins, some fighters (the F-4, for example) had a problem with adverse yaw when making aileron inputs at high angle of attack (AOA). In this situation, the aileron on the wing going up produced enough drag to pull that wing "back" as the jet rolled...the result was a tendency to roll in one direction while yawing in the opposite direction. If this condition was aggrevated enough, the outcome was a 'departure' (uncontrolled pitching, yawing, and rolling) that could end up in a spin if not corrected.

You sure that this is really correct? I think the problem is rather due to insufficient yaw authority. Have to look it up, but the "drag" of the aileron (it is more the entire wing) shouldn't be the big issue when vertical stabilizer is in the loop.

luca
29th October 2010, 14:07
Sure it is correct.
Most fighters are directionally unstable above 15-20 deg AOA even without roll input. Fortunately lateral stability helps.
During aileron rolls, 4.th gen. fighter's ARI adds rudder automatically for rolling...

"At speeds and alphas close to stall, typical supersonic fighter response to aileron input is opposite - left stick produces roll to the right. Down going, right aileron generates more drag than left aileron and aircraft sideslips to the right – “adverse yaws”. Roll moment of the sideslip (lateral stability)overpowers aileron’s roll moment. In that case rudder is more effective for roll control. At some higher α rudder effectiveness diminishes and lateral controls can be used for directional control. That means if one wants to roll, up to 10-20º α it would use ailerons, after that rudders are safer and more effective (either one can force the aircraft to the spin) and at higher α, where rudder lose effectiveness, opposite aileron can be only yaw and thus roll control." ....source:

http://cgi.ebay.com/Fighter-Performance-in-Practice-F-4-Phantom-vs-MIG-21_W0QQitemZ290490431752QQcategoryZ2228QQcmdZViewI temQQ_trksidZp4340.m444QQ_trkparmsZalgo%3DCRX%26it s%3DC%252BS%26itu%3DSI%252BUA%252BLM%252BLA%26otn% 3D5%26ps%3D63%26clkid%3D4815990259887496461

Aircraft can be designed laterally unstable for max roll rate and acceleration, but dynamic directional stability would suffer, besides constant need for lateral trimming.
Upper graph depicts response to roll command for pure lateral controls and for one refined with Command Augmentation System / ARI.
Lower diagram shows roll rate vs static longitudinal stability (usual +2% to -10%). Roll rate decay with increased longitudinal instability is because of need to arrest more pronounced inertial coupling.

alfakilo
29th October 2010, 18:05
You sure that this is really correct? I think the problem is rather due to insufficient yaw authority. Have to look it up, but the "drag" of the aileron (it is more the entire wing) shouldn't be the big issue when vertical stabilizer is in the loop.

Yes, I am sure that is correct.

Here is a link to a USN F-4 flight manual (see chapter 4, Flight Characteristics):

http://books.google.com/books?id=oeJuJtjK4k0C&pg=SA4-PA2&lpg=SA4-PA2&dq=unload+for+control+adverse+yaw&source=bl&ots=NYfrrnnjOQ&sig=yn72YUbps7ZLEIiNIL9zIFdUPOY&hl=en&ei=QQnLTLCAJIG8lQeF5v2yAQ&sa=X&oi=book_result&ct=result&resnum=8&ved=0CDMQ6AEwBw#v=onepage&q&f=false

On page 4-2, adverse yaw is discussed.

On page 4-5, loss of control.

On page 4-8, a discussion of "Asymmeteric Load Effects" ( basically describes the perils of rolling pulling g at the same time).

wolfhound
31st October 2010, 16:49
The Super Hornet has a maximum roll rate of 225 deg/s as has already been mentioned. The F-16 has a maximum roll rate of 240 deg/s and the Rafale has a maximum roll rate of 270 deg/s.
The A-4 has a very high max roll rate, I think 720 deg/s +. However this is only attained after two or more continuous rolls through 360 degrees.