View Full Version : Aerobatics Slow Rolls
Hi,
Not sure if this is the right forum to ask but something has been bothering me recently. The IAC states for aerobatics:
Slow rolls have to be flown normally on a straight line (exception is the avalanche). The roll rate has to be constant and the longitudinal axis of the plane has to go straight.
How can you fly the aircraft along a straight line and also keep the longitudinal axis of the aircraft straight. I would have thought that the less efficient fuselage lift in the knife-edge portion of flight would necessitate a higher angle of attack to maintain 1 g lift in the vertical. Thus requiring the longitudinal axis of the airplane to be tilted. Can someone clarify this for me.
J
Agaricus bisporus
21st Oct 2010, 13:28
You are right, of course, the longitudinal axis of the aeroplane must change during the roll as you've stated. I think what the description means to say is that the axis of the flightpath during the roll must remain straight.
Look at it as the longitudinal axis along which the aircraft motion takes place?
Strange wording - is that a translation?
stiknruda
21st Oct 2010, 15:12
It is an axial roll - the a/c CoG should translate smothly along the longitudinal axis.
bearfoil
21st Oct 2010, 16:11
Forget the rules, what is the ball doing?
It depends on how tight your straps are - oh - sorry, I see what you mean..............................
fantom
21st Oct 2010, 16:19
Forget the rules, what is the ball doing?
Only one, BOAC? Adolf was the same, according to the song.
Checkboard
21st Oct 2010, 16:32
The balance ball? On a slow roll it's providing no useful information whatsoever. :hmm:
"Adolf was the same, according to the song."
Goebbels would be lost IMC?
Don't know about IAC, but here's a very good summary of competition aerobatic judging which should tell you all you want to know (slow rolls are on page 9):Judging - Centre of Gravity Track (http://www.aerobatics.org.uk/judging/judging-cgt.htm)
fantom
21st Oct 2010, 18:59
Goebbels would be lost IMC
Correct, but Göring could probably manage in light Cu.
Ulysses05
22nd Oct 2010, 01:24
Removing this post after reading Deefer Dog's comments. Thanks for the correct inputs. Maybe one day, you can teach me slow rolls! :)
deefer dog
22nd Oct 2010, 09:07
Ulysses, I beg to differ.
First, the manouvre you describe is actually an"aileron roll" which bears only a passing resemblance to a "slow roll." In competition, the slow roll should be flown without gain or loss of altitude, and certainly without any initial pitch up that you mention, or it would be heavily penalised by the judges.
Most types certified for aeerobatics will fly the manouvre, but success depends on piloting skill. As a general rule of thumb, if you can slow roll a Tiger Moth (circa 1930, with almost non existant ailerons, and no inverted fuel system), you can slow roll anything.
DB6's post is good reading on the subject.
stiknruda
22nd Oct 2010, 10:24
DB6's post is good reading on the subject.
That's because DB6 and I used to compete against each other years ago!! And his slow-roll was painfully slow as befitted a craft with long wings:ok:
Bet his 'cadets' are not winning many prizes for slow rolls:)
Even slower nowdays, Stik. Try a Grob Heron (lower-powered, fixed pitch Tutor) - I keep telling my students to think of them as axial rolls; roll as fast as you can, they'll still be slow in this thing. You Pitts guys have it pitts-easy ! :E
Ulysses05
27th Oct 2010, 17:20
I stand corrected. Thanks for pointing out the difference between an aileron roll and a slow roll. I guess with the limited power of the trainer I flew, I could never have aimed for a slow roll as flown by the pure aerobats. And yes BOAC, my former students will never win an aerobatic championship.. they're too busy whooping British ass in Exercise Indradhanush back in India.
I say, I hope you mean 'whopping British arse' old chap. I don't think I've ever whooped an ass of any nationality.
I suspect our Typhoos will wax a few backsides, actually (that's 'kick some asses'):)
- especially if we can encourage them to fall out of a few slow rolls.....................
Ulysses05
27th Oct 2010, 18:04
Ah! Language!! I shall concede that to you since you guys taught us the language anyway! I'm looking at the Typhoon with some interest too. Guess they want to sell some to the Indians, that's why they are there.
Checkboard
27th Oct 2010, 19:10
I thought that if the roll took more than 15 seconds it was a "super slow roll"? ;)
Wizofoz
27th Oct 2010, 19:29
Checkie- Only if it involves you, Red and a soft surface!!
Actually, in FAI terms, there IS no "Slow roll". A roll is a 360 rotation around the logitudinal axis, and rate is never considered. You may be thinking about Model aircraft.
While it's true that "Rolling around the CG" may be the ideal talked about in the Judges notes, being able to keep the aircraft as horizontal as possible will always score better.
It was similar with Vertical Lines. The judges were supposed to take into consideration the lift a flat-bottom wing would produce, imagine the nil-wind attitude that would require to track exactley vertically, then apply the wind to that.
FACT was, point the thing such that the fuselarge was straight up, and no judge could tell the difference!!