F-104 : rolling
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Mark,
All though the phenomenon was fairly new at the time, I think Kelly Johnson took the inertia coupling into account while designing the 104. The large vertical fin and the high placement of the horisontal tail alleviated the problem.
Although I am not sure if it had any limitations in the Dash-1 regarding roll rate and consecutive rolls, I have a copy laying around somewhere, and if I can find it I will try to look it up.
All though the phenomenon was fairly new at the time, I think Kelly Johnson took the inertia coupling into account while designing the 104. The large vertical fin and the high placement of the horisontal tail alleviated the problem.
Although I am not sure if it had any limitations in the Dash-1 regarding roll rate and consecutive rolls, I have a copy laying around somewhere, and if I can find it I will try to look it up.
I don't own this space under my name. I should have leased it while I still could
Certainly a BAF pilot used to do rolls along the runway during air displays. Usually level at 50 feet or less clean. With undercarriage down he would touch, bounce, roll, touch, bounce, roll.
Impressive if viewed from behind at a safe distance.
Impressive if viewed from behind at a safe distance.
Don't know about the 104 but I remember being taught that fast jet some types of that era (possibly including one I flew, memory fails me on the specifics) had a limitation on the number of consecutive rolls, ( a possible limitation F-16GUY has mentioned) to stop the effect of inertia coupling building up and becoming err, to say the least, nasty. So for example one might be allowed no more than one continuous 360 roll at a time only.. .Since the BAF pilot was stopping rolling to do his "bumps" he'd be complying with that type of limitation.
Last edited by wiggy; 10th Mar 2017 at 07:28.
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Flew with a few ex Luftwaffe guys...one story was how few rolls one could do applying full aileron whilst flat out....and immediately centring the stick ...four and a quarter.
Don't disbelieve the guy as I mentioned putting the seat belt signs on in light chop..DC9-51 in cruise.....he looked me in the eyes...Turbulenz Alan...shoved the stick fully forward..then fully aft..."das ist turbulenz alan".
I was instantly white and wet.
Ironically he had a heart problem a few months later and was put in charge of FDR analysis.
Don't disbelieve the guy as I mentioned putting the seat belt signs on in light chop..DC9-51 in cruise.....he looked me in the eyes...Turbulenz Alan...shoved the stick fully forward..then fully aft..."das ist turbulenz alan".
I was instantly white and wet.
Ironically he had a heart problem a few months later and was put in charge of FDR analysis.
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Skyhawk A-4E/F/G NATOPS has this caution (for the initially unnerving 720 degree per second roll rate at best roll speed of 250 KIAS).
"Aileron Rolls
During and upon termination of high rate aileron rolls (above 200 degrees per second) in the high speed, low altitude region, abrupt pitchdown will be noted. This pitchdown, though uncomfortable, is structurally safe and aircraft structure limits will not be exceeded provided that 360 degrees of roll are not exceeded.
CAUTION
When executing high rate, low altitude rolls (above 200 degrees per second), recovery controls must be applied after completing 180 degrees of roll to prevent exceeding 360 degrees of roll."
During and upon termination of high rate aileron rolls (above 200 degrees per second) in the high speed, low altitude region, abrupt pitchdown will be noted. This pitchdown, though uncomfortable, is structurally safe and aircraft structure limits will not be exceeded provided that 360 degrees of roll are not exceeded.
CAUTION
When executing high rate, low altitude rolls (above 200 degrees per second), recovery controls must be applied after completing 180 degrees of roll to prevent exceeding 360 degrees of roll."
Wasn't roll coupling potential that predicated Fuse 31(?) in the Gnat, ie to limit rate of roll. I thing the Reds disabled/removed the fuse.....now what did I have for breakfast?
I don't own this space under my name. I should have leased it while I still could
Golfer, that's the guy. As far as I recall he did more than one touch per pass.
Wiggy, his high speed rolls were below the touch roll apogee and multiple.
Wiggy, his high speed rolls were below the touch roll apogee and multiple.
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Wander00
Yes, you are quite right. That's just what they did until an SHP who's name escapes me at this distance in time was practicing for the Wright Jubilee in front of the AOC etc. He, too, had removed the fuse. Got roll/yaw coupling at display centre. The aircraft literally tore itself to pieces. The Arrows put their fuses back the same afternoon!
Yes, you are quite right. That's just what they did until an SHP who's name escapes me at this distance in time was practicing for the Wright Jubilee in front of the AOC etc. He, too, had removed the fuse. Got roll/yaw coupling at display centre. The aircraft literally tore itself to pieces. The Arrows put their fuses back the same afternoon!
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This is how it looks in the HUD of a Hornet during testing:
https://www.youtube.com/watch?v=wZNaQuUGluk
https://www.youtube.com/watch?v=wZNaQuUGluk
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At the Biggin Hill BoB weekend in 1975 there were two Dutch 104s displaying. On the Monday morning, as we were saying farewell to the visiting aircraft, the Cloggies came out and told us to watch their departure . . . .
They took off as a pair and then, having kept it on the deck heading towards the famous "bump", the no.2, as they were approaching the threshold, rolled over the leader and INTO the dip beyond the runway, before climbing out!!!
They took off as a pair and then, having kept it on the deck heading towards the famous "bump", the no.2, as they were approaching the threshold, rolled over the leader and INTO the dip beyond the runway, before climbing out!!!
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I remember those A-4 roll warnings and cautions. I also remember the Blues doing a 720 degree per second roll for several revolutions while in a steep climb. I understand (but do not know) they were able to do this by unloading the aircraft just prior to initiating the roll.
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The Kiwi A-4K KAHU Demo Pilot would do the same spouting those bright thingos meanwhile. There is a video somewhere of the demo in Kiwiland. The start of this video shows the upward roll aftermath, the end of the previous part shows the same (screenshot) - this time no flares popped - demo singleton did this I think.
Last edited by SpazSinbad; 10th Mar 2017 at 13:16. Reason: screenshot & video
Wiki has this to say about the F104:
The stabilator (horizontal tail surface) was mounted atop the fin to reduce inertia coupling. Because the vertical fin was only slightly shorter than the length of each wing and nearly as aerodynamically effective, it could act as a wing on rudder application, rolling the aircraft in the opposite direction of rudder input. To offset this effect, the wings were canted downward, giving 10° anhedral.
A ventral fin was also added fairly early on in the programme.
The stabilator (horizontal tail surface) was mounted atop the fin to reduce inertia coupling. Because the vertical fin was only slightly shorter than the length of each wing and nearly as aerodynamically effective, it could act as a wing on rudder application, rolling the aircraft in the opposite direction of rudder input. To offset this effect, the wings were canted downward, giving 10° anhedral.
A ventral fin was also added fairly early on in the programme.
F-104S Manual
AILERON AND RUDDER TRAVEL LIMITING SYSTEM
Aileron and rudder travel is limited automatically when the gear is UP, and unlimited when the gear is DOWN. With gear DOWN, aileron travel is approximately +-20° and with gear UP, aileron travel is approximately +-10°. An additional 5° of aileron travel may be obtained with gear UP by using aileron trim.
With gear DOWN, rudder travel is 20° (+-2°) to either side of neutral and with the gear UP, rudder travel is limited to 6° either side of neutral. An additional 4° of rudder travel is available with gear UP if rudder trim is used. Aileron and rudder limiting circuit is powered by the PP2 DC bus. If electrical failure occurs, rudder and aileron travel will not be limited.
Pulling the RUD/AIL LIMIT CONT circuit breaker, on the left console, will remove the rudder and aileron travel limiters (refer to Section VI "Flight Characteristics" for additional information on this system).
Aileron and rudder travel is automatically unlimited when gear is DOWN or when gear is UP and a flaps asymmetry condition exists as detected by the flaps asymmetry detection system. When the aileron and rudder travel is unlimited, a warning light on the main instrument panel illuminates.
WARNING
THE USE OF FULL UNLIMITED AILERON OR RUDDER TRAVEL IN MANEUVERS AT SPEEDS ABOVE 300 KIAS MAY RESULT IN STRUCTURAL DAMAGE AND POSSIBLE LOSS OF THE AIRCRAFT.
AILERON ROLL LIMITATIONS
In order to avoid inertial coupling and high structural loads approaching limit values, aileron rolls are subject to the following restrictions:
WING FLAPS RETRACTED
Entry Load Factor of 0.5 "G" and Greater
Full deflection rolls are limited to 360°. Below l "G” with pitch or yaw stability augmenters inoperative, full deflection 360° rolls are prohibited.
Entry Load Factor Less Than 0.5 "G”
Full deflection 360° rolls are prohibited. All rolls below 0.5 "G” load factor shall be executed with extreme caution.
NOTE
Application of some back stick pressure during roll helps to terminate the roll more rapidly and make a smoother transition to normal ilight.
AILERON ROLLS
Aileron roll characteristics within the prescribed limits are excellent. Because of inertial coupling tendencies peculiar to all supersonic configurations, certain restrictions on rolling maneuvers have been imposed to prevent loss of control and/or exceeding structural limits.
These inertial coupling tendencies result from the large pitch and yaw inertia of the supersonic configurations and the angular relationship of the longitudinal inertia axis of the aircraft with the axis of rotation. This angular relationship varies with flight conditions (speed, altitude and load factor). Depending on whether the inertia axis is nose-up or nose·down relative to the flight path or rolling axis, a sideslip is developed during a roll which produces inhibiting or augmenting roll rate. In extreme cases, if sufficient aileron control power is allowed, this divergent type roll rate due to sideslip may result in excessive rolling velocity, uncontrollable, rolls or damage and failure.
ln order tn remain within safe limits. the available aileron travel is reduced with gear up to prevent high roll rates. ln addition, the amount of continuous rotation is placarded in all configurations to prevent large amounts of sideslip from developing.
http://www.916-starfighter.de/F-104_...20Coupling.pdf
AILERON AND RUDDER TRAVEL LIMITING SYSTEM
Aileron and rudder travel is limited automatically when the gear is UP, and unlimited when the gear is DOWN. With gear DOWN, aileron travel is approximately +-20° and with gear UP, aileron travel is approximately +-10°. An additional 5° of aileron travel may be obtained with gear UP by using aileron trim.
With gear DOWN, rudder travel is 20° (+-2°) to either side of neutral and with the gear UP, rudder travel is limited to 6° either side of neutral. An additional 4° of rudder travel is available with gear UP if rudder trim is used. Aileron and rudder limiting circuit is powered by the PP2 DC bus. If electrical failure occurs, rudder and aileron travel will not be limited.
Pulling the RUD/AIL LIMIT CONT circuit breaker, on the left console, will remove the rudder and aileron travel limiters (refer to Section VI "Flight Characteristics" for additional information on this system).
Aileron and rudder travel is automatically unlimited when gear is DOWN or when gear is UP and a flaps asymmetry condition exists as detected by the flaps asymmetry detection system. When the aileron and rudder travel is unlimited, a warning light on the main instrument panel illuminates.
WARNING
THE USE OF FULL UNLIMITED AILERON OR RUDDER TRAVEL IN MANEUVERS AT SPEEDS ABOVE 300 KIAS MAY RESULT IN STRUCTURAL DAMAGE AND POSSIBLE LOSS OF THE AIRCRAFT.
AILERON ROLL LIMITATIONS
In order to avoid inertial coupling and high structural loads approaching limit values, aileron rolls are subject to the following restrictions:
WING FLAPS RETRACTED
Entry Load Factor of 0.5 "G" and Greater
Full deflection rolls are limited to 360°. Below l "G” with pitch or yaw stability augmenters inoperative, full deflection 360° rolls are prohibited.
Entry Load Factor Less Than 0.5 "G”
Full deflection 360° rolls are prohibited. All rolls below 0.5 "G” load factor shall be executed with extreme caution.
NOTE
Application of some back stick pressure during roll helps to terminate the roll more rapidly and make a smoother transition to normal ilight.
AILERON ROLLS
Aileron roll characteristics within the prescribed limits are excellent. Because of inertial coupling tendencies peculiar to all supersonic configurations, certain restrictions on rolling maneuvers have been imposed to prevent loss of control and/or exceeding structural limits.
These inertial coupling tendencies result from the large pitch and yaw inertia of the supersonic configurations and the angular relationship of the longitudinal inertia axis of the aircraft with the axis of rotation. This angular relationship varies with flight conditions (speed, altitude and load factor). Depending on whether the inertia axis is nose-up or nose·down relative to the flight path or rolling axis, a sideslip is developed during a roll which produces inhibiting or augmenting roll rate. In extreme cases, if sufficient aileron control power is allowed, this divergent type roll rate due to sideslip may result in excessive rolling velocity, uncontrollable, rolls or damage and failure.
ln order tn remain within safe limits. the available aileron travel is reduced with gear up to prevent high roll rates. ln addition, the amount of continuous rotation is placarded in all configurations to prevent large amounts of sideslip from developing.
http://www.916-starfighter.de/F-104_...20Coupling.pdf
Trust me to reverse the digits. Must try harder. Reading this and the thread connected above leads me to wonder how I ever managed to fly the blooming thing, but I did and like many others LOVED it