snap rolls and other flick manoeuvres
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snap rolls and other flick manoeuvres
Following on from some of the aside comments on the 'Tiger Moth' forum, snap rolls and other 'flick' manoeuvres if conducted below the design manoeuvring speed (Va), SHOULD NOT result in aerodynamic deformation of the aircraft structure.
Having said that, it is worthwhile reminding ourselves about what is achieved during certification flight test.
The handling tip sheets called for the aircraft to be established in a 'steady state slide slip' via the application of full left rudder followed at some point by the same test to the right. You are looking at controllability, control forces and for some other less known things now like 'rudder lock over'. The DC 3 for instance suffers this problem.
What the test sheets do NOT call for is the application of full left rudder followed immediately be the application of full right rudder. The resultant forces created by inertia etc can easily exceed the design limit load of the rudder and empennage.
AA 587 comes to mind.
So, as the NTSB said in its report, Va must be given some respect and may in fact be too optimistic a speed for full control deflection.
Va, or 'corner velocity' in military fighter terms, varies with the configuration and other factors such that aerobatic aeroplanes that have manoeuvring devices such as slats, have a different Va for different configurations within the flight envelop.
Easy to work out; the minimum speed at which you can pull a certain amount of 'g' is given by the formula; Vsg1 x Square root of the 'g'.
Vsg1: 80 kts; to pull 4 'g' min CAS; 160knots.
Staying closer to those speeds rather than a straight flight manual number should give a margin to structural failure with any conventional manoeuvre.
This is a big topic as we know and I have glossed over some model specific issues such as wing form; control surface volume etc.
Still would not flick roll/ snap roll a Decathlon at any great speed if at all.
Having said that, it is worthwhile reminding ourselves about what is achieved during certification flight test.
The handling tip sheets called for the aircraft to be established in a 'steady state slide slip' via the application of full left rudder followed at some point by the same test to the right. You are looking at controllability, control forces and for some other less known things now like 'rudder lock over'. The DC 3 for instance suffers this problem.
What the test sheets do NOT call for is the application of full left rudder followed immediately be the application of full right rudder. The resultant forces created by inertia etc can easily exceed the design limit load of the rudder and empennage.
AA 587 comes to mind.
So, as the NTSB said in its report, Va must be given some respect and may in fact be too optimistic a speed for full control deflection.
Va, or 'corner velocity' in military fighter terms, varies with the configuration and other factors such that aerobatic aeroplanes that have manoeuvring devices such as slats, have a different Va for different configurations within the flight envelop.
Easy to work out; the minimum speed at which you can pull a certain amount of 'g' is given by the formula; Vsg1 x Square root of the 'g'.
Vsg1: 80 kts; to pull 4 'g' min CAS; 160knots.
Staying closer to those speeds rather than a straight flight manual number should give a margin to structural failure with any conventional manoeuvre.
This is a big topic as we know and I have glossed over some model specific issues such as wing form; control surface volume etc.
Still would not flick roll/ snap roll a Decathlon at any great speed if at all.
The FAA's SAIB with added notes here http://www.safepilots.org/documents/...ring_Speed.pdf give the best explanation of Va - max speed for snaps is generally well below that as explained in that document.
CASA's CAAP 155-1 is dangerously deficient in its explanation of Va as well as limitations on control application above Va.
Anyway, I'm off to do some aerobatics in a Super Decathlon. I'll go in the Tiger if offered a ride.
CASA's CAAP 155-1 is dangerously deficient in its explanation of Va as well as limitations on control application above Va.
Anyway, I'm off to do some aerobatics in a Super Decathlon. I'll go in the Tiger if offered a ride.
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Djpil,
Fully agree; the CAAP is a very simplistic document with some questionable aerodynamic comments. 'Stick position' for stall indication? Hmm, still mulling over that one.
The FAA document is fulsome.
Enjoy the Super Decathlon: 'Super' is a great word that I always look for in the name of a possible aerobatic steed.
I know of no aircraft that suffers from an excess of power in the aerobatic sphere.
Fully agree; the CAAP is a very simplistic document with some questionable aerodynamic comments. 'Stick position' for stall indication? Hmm, still mulling over that one.
The FAA document is fulsome.
Enjoy the Super Decathlon: 'Super' is a great word that I always look for in the name of a possible aerobatic steed.
I know of no aircraft that suffers from an excess of power in the aerobatic sphere.
Folks,
Can't find my old Pilots Notes, but I recall that flick maneuver were not permitted in a DH82.
They were certainly prohibited in a DHC-1 Chipmunk, and I have seen two severely damaged (fuselage behind the back seat wrinkled) from idiots ignoring the Flight Manual.
Indeed, you can take it that flick maneuvers are prohibited by certification standards, unless they are specifically permitted by the AFM.
Tootle pip!!
Can't find my old Pilots Notes, but I recall that flick maneuver were not permitted in a DH82.
They were certainly prohibited in a DHC-1 Chipmunk, and I have seen two severely damaged (fuselage behind the back seat wrinkled) from idiots ignoring the Flight Manual.
Indeed, you can take it that flick maneuvers are prohibited by certification standards, unless they are specifically permitted by the AFM.
Tootle pip!!
Over the past 25 years I've flown / operated several Tigers. The word "not" has been omitted from "Flick manoeuvres are not permitted" statement in some of the CASA (DCA, DOTC, etc) Approved Flight Manuals. I did report this to my local CASA district office, however as quick as a flash no action was taken. When on holidays a few years ago I watched some keen Tiger pilot doing avalanches (snap roll at the top if a loop) with fare paying passengers on board. I contacted the operator to suggest this wasn't such a great idea and was promptly told to mind my own business.
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DH 82
The thing about porteous loops / avalanches is that the aircraft must be in balanced flight at the top of the loop. For the 'flick' portion of the manoeuvre, existing yaw can produce markedly different results to those expected when the rudder is introduced particularly if the yaw is in the 'direction' of the engine and you opt to flick in that direction as well.
Couple that with biplane characteristics: two seperate wings with different sweep back, different manoeuvre margins for each wing and a heavy dose of difficulty (for some pilots and I will include myself) in keeping the aircraft balanced in all three axis as one climbs up the loop with reducing airspeed etc, etc and the entry conditions are likely to be different most times.
The prohibition on 'flick' manoeuvres for the DH82 is understandable from the aerodynamic forces perspective even given that 'wood' is better than metal in some respects, but it is also understandable from the piloting aspects.
Not all high speed autorotations, i.e. high speed spins, are predictable in their outcomes. The speed loss is dramatic in a flick manoeuvre and when you do not have a lot of airspeed available to start with (typically no more than double the stall speed), this is a testing manoeuvre to execute regularly with the same outcome.
As for doing an avalanche with fare paying passengers in a DH 82, discretion seems to have gone astray.
Couple that with biplane characteristics: two seperate wings with different sweep back, different manoeuvre margins for each wing and a heavy dose of difficulty (for some pilots and I will include myself) in keeping the aircraft balanced in all three axis as one climbs up the loop with reducing airspeed etc, etc and the entry conditions are likely to be different most times.
The prohibition on 'flick' manoeuvres for the DH82 is understandable from the aerodynamic forces perspective even given that 'wood' is better than metal in some respects, but it is also understandable from the piloting aspects.
Not all high speed autorotations, i.e. high speed spins, are predictable in their outcomes. The speed loss is dramatic in a flick manoeuvre and when you do not have a lot of airspeed available to start with (typically no more than double the stall speed), this is a testing manoeuvre to execute regularly with the same outcome.
As for doing an avalanche with fare paying passengers in a DH 82, discretion seems to have gone astray.
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And I forgot to add, if the nose drops further than the pilot expects during the inverted portion of the manoeuvre and the roll entry has been marked, there is a natural tendency to correct this situation with opposite rudder.
If the initiating rudder input has been maintained, THEN you can easily get into a 'stop to stop' complete deflection of the rudder which leads to the problems I mentioned at the start of this post.
Stay safe.
If the initiating rudder input has been maintained, THEN you can easily get into a 'stop to stop' complete deflection of the rudder which leads to the problems I mentioned at the start of this post.
Stay safe.
Aaaah, the great flight manual debacle - of course CASA would take no action on flight manuals because they withdrew their flight manuals and there is therefore none for the Tiger.
The current issue of the CAAP is of July 2000 so we are still waiting although I see that there is a draft AC. No hurry is there.
It'd be interesting to see what is supposed to be on the operating limitations placard for the Tiger but I guess per my original pilot's notes (cost 50 p). I recall something in Neil Williams' book about flick rolls having an immediate adverse effect on the wing rigging.
As for certification standards - worth noting the plural and not all of the older ones are similar to the current FAR 23. FAA AC 91-48 has useful advice including:
Disappointing the number of Decathlon (as an example given that it is a popular aerobatic trainer) aerobatic pilots I encounter who have never read the Flight Manual, especially the Limitations Section. One assured me that he knew where the Flight Manual was! The same ones don't bother reading placards and often claim ignorance of their existence.
Update - 30 October 2009
.......
CAAP 54-1 will is also be updated to remove the requirement to obtain a CASA Flight Manual Approval Page.
.......
CAAP 54-1 will is also be updated to remove the requirement to obtain a CASA Flight Manual Approval Page.
It'd be interesting to see what is supposed to be on the operating limitations placard for the Tiger but I guess per my original pilot's notes (cost 50 p). I recall something in Neil Williams' book about flick rolls having an immediate adverse effect on the wing rigging.
As for certification standards - worth noting the plural and not all of the older ones are similar to the current FAR 23. FAA AC 91-48 has useful advice including:
If acrobatics are planned, be sure your aircraft is certificated in the “acrobatic" category. Section 23.3(c) states, “The acrobatic category is limited to airplanes intended for use without restrictions other than those shown to be necessary as a result of required flight tests. This does not mean that all acrobatic maneuvers can be flown. Operating limitations must be observed.
Last edited by djpil; 3rd Jan 2016 at 08:25. Reason: Clarify Neil's comment
Leadie:
I think you're possibly getting this from a club manual? Semantics I know, but they're certainly not specifically prohibited (or even mentioned) in the Chipmunk AFM, they're just not included in the list of approved manouvres.
My 1966 copy of the RAF Pilot's Notes (A.P.4308 A-P. N.) merely states "Aerobatics are permitted but inverted flying is prohibited", while my 1969 (RAF) Chipmunk Study Guide (TC/250262) merely describes how to fly various aerobatic manouvres (but not any flick manouvres/snap rolls). The latter has no limitations or prohibitions mentioned at all.
I'm with you though - you'd have to be nuts to do this in a Chipmunk.
Cheers.
They were certainly prohibited in a DHC-1 Chipmunk
My 1966 copy of the RAF Pilot's Notes (A.P.4308 A-P. N.) merely states "Aerobatics are permitted but inverted flying is prohibited", while my 1969 (RAF) Chipmunk Study Guide (TC/250262) merely describes how to fly various aerobatic manouvres (but not any flick manouvres/snap rolls). The latter has no limitations or prohibitions mentioned at all.
I'm with you though - you'd have to be nuts to do this in a Chipmunk.
Cheers.
Ultralights, as some-one who likes snap rolls you should really get into a Pitts. I won't post any recent videos of my snaps so just noting a memory of three of us doing formation snaps - similar to this but not quite as close and nowhere near that low (see the first 30 secs)
Last edited by djpil; 3rd Jan 2016 at 23:45. Reason: Fixed link to Utube
Many years ago I was fortunate (or unfortunate[?]) enough to find myself with access to a brand new C150 Aerobat. Having completed a basic aerobatic endorsement in that aeroplane I decided to teach myself snap rolls - so off I went, climbed to a "safe" height with Aerobat in one hand and Cessna POH in the other, opened at the section on snap rolls.
Pre-aerobatic checks complete, I initiated a by-the-book snap roll entry ..................... and the world as I knew it went beserk!
I recovered from the spin after several turns and many hundreds of feet below where I had started!
So much for snap rolls - I resolved there and then to never do that again!
Dr
PS:Several years later I was somewhat surprised to see little brackets strengthening the tail of the C150A - the result of a mandatory AD.
Pre-aerobatic checks complete, I initiated a by-the-book snap roll entry ..................... and the world as I knew it went beserk!
I recovered from the spin after several turns and many hundreds of feet below where I had started!
So much for snap rolls - I resolved there and then to never do that again!
Dr
PS:Several years later I was somewhat surprised to see little brackets strengthening the tail of the C150A - the result of a mandatory AD.
I was nearly going to mention the Cessna Aerobat, it does magnificent snaps. I suggest that you take this book with you when you try it next time: The Flight Manual Series - William K Kershner
I was nearly going to mention the Cessna Aerobat, it does magnificent snaps.
Around the same time I attended an airshow at Coolangatta where I saw a Pitts Special perform for the first time, along with Barry Hempel in the Super Decathalon and an Aerobat. The Pitts was spectacular, the Decathalon was polished, but the Aerobat impressed me the most because I had some understanding of the limitations of the aircraft. Can't remember who the pilot was but he did a number of low passes down the runway followed by a 45o pitch up with a snap roll at about 200 feet AGL. Given my own disasterous experience with snap rolling the Aerobat, I was blown away by that!
Some years later I found myself in an Aerobat with one Warwick Bleakley, who will be known to some of our Kiwi bretheren on here, for a flour bombing competition at the Manawatu Districts Aero Club. After completing my bombing run Warwick asked, "Do you mind if I have a bit of fun now"? My hesitant, "OK" was followed by a series of very precise snap rolls!
Dr
rjtjrt, I'd certainly recommend Kershner's book for anyone learning in an Aerobat (a great basic aerobatic trainer in my opinion). https://books.google.com.au/books?id...s_similarbooks
Learning on a Decathlon I'd go for http://www.amazon.com.au/Aerobatics-Super-Decathlon-David-Pilkington-ebook/dp/B00PH1NY6Y/ref=sr_1_9?s=digital-text&ie=UTF8&qid=1415779204&sr=1-9&keywords=aerobatics (Kindle e-book) and https://www.createspace.com/5108886?ref=1147694&utm_id=6026 for the paperback
or perhaps Bob Tait's new book Bob Tait's Aviation Theory School - Aerobatics and Tailwheel Flying (Book only)
Neil Williams' book is dated but great reading https://books.google.com.au/books?id...s_similarbooks
To go further I'd recommend Alan Cassidy's Better Aerobatics Book by Alan Cassidy
Dave Robson's book is fine too Aerobatics - Principles and Practice - Aviation Theory Centre Aviation Theory Centre
Dave's book replaced the 1990 book Flying Aerobatics by Robert T. Bowring which is based on the Chipmunk. It mentions the flick (or snap) roll "conducted only in those aircraft which have been specifically cleared for the Flick Roll then goes on to explain how to do snap rolls with excellent diagrams of the Chipmunk.
Of course, Stan's book https://books.google.com.au/books/ab...AJ&redir_esc=y for those who might be learning in an Airtourer. Reminds me when I arranged for the Airtourer to be approved for snaps back in the '70s - another story for later.
Learning on a Decathlon I'd go for http://www.amazon.com.au/Aerobatics-Super-Decathlon-David-Pilkington-ebook/dp/B00PH1NY6Y/ref=sr_1_9?s=digital-text&ie=UTF8&qid=1415779204&sr=1-9&keywords=aerobatics (Kindle e-book) and https://www.createspace.com/5108886?ref=1147694&utm_id=6026 for the paperback
or perhaps Bob Tait's new book Bob Tait's Aviation Theory School - Aerobatics and Tailwheel Flying (Book only)
Neil Williams' book is dated but great reading https://books.google.com.au/books?id...s_similarbooks
To go further I'd recommend Alan Cassidy's Better Aerobatics Book by Alan Cassidy
Dave Robson's book is fine too Aerobatics - Principles and Practice - Aviation Theory Centre Aviation Theory Centre
Dave's book replaced the 1990 book Flying Aerobatics by Robert T. Bowring which is based on the Chipmunk. It mentions the flick (or snap) roll "conducted only in those aircraft which have been specifically cleared for the Flick Roll then goes on to explain how to do snap rolls with excellent diagrams of the Chipmunk.
Of course, Stan's book https://books.google.com.au/books/ab...AJ&redir_esc=y for those who might be learning in an Airtourer. Reminds me when I arranged for the Airtourer to be approved for snaps back in the '70s - another story for later.
the Aerobat impressed me the most ..... Can't remember who the pilot was ....
Dora-9,
Not so, I don't have the original documentation that I had in early 60's, (in the UK) but the prohibition was quite specific, due to demonstrated damage to aircraft.
This raises the issue of the original RAF Pilots Notes, (and much other similar military paperwork) permitted manoeuvers are listed, if they are not listed they are not permitted. Perhaps part of the answer is to be found in the RAF definition of "aerobatic".
On that basis, what I have said, and your post are consistent.
You will find the same thing in many US military manuals, NATOPS etc., permitted manoeuvers are listed.
As for civil aircraft, especially C-152 and similar, limiting G-loads on the structure are not based on "rolling G", what sort of an answer would you get if you asked many pilots what allowance you would make for "rolling G"??
Tootle pip!!
Not so, I don't have the original documentation that I had in early 60's, (in the UK) but the prohibition was quite specific, due to demonstrated damage to aircraft.
This raises the issue of the original RAF Pilots Notes, (and much other similar military paperwork) permitted manoeuvers are listed, if they are not listed they are not permitted. Perhaps part of the answer is to be found in the RAF definition of "aerobatic".
On that basis, what I have said, and your post are consistent.
You will find the same thing in many US military manuals, NATOPS etc., permitted manoeuvers are listed.
As for civil aircraft, especially C-152 and similar, limiting G-loads on the structure are not based on "rolling G", what sort of an answer would you get if you asked many pilots what allowance you would make for "rolling G"??
Tootle pip!!
Leadie:
I think we're singing from the same hymn book here!
As I said, the RAF Pilot's Note are delightfully vague, whereas the AFM (now the "last word") simply lists permitted manouvres.
At the risk of digressing (Who? Me?), I'm always intrigued how items appeared in club handling notes and how they eventually become set in concrete, yet no-one can tell you why. I started in Chipmunks in the early 1960's, the club notes specifically banned side-slips with full flap. It was simply verboten without qualification, and God help you if you even thought of doing this. Querying this, I was given a variety of frightening reasons (the aircraft would flick into a vicious spin/the flaps would fall off etc), yet there is no such prohibition in either the AFM or RAF Pilot's Notes. Indeed the Study Guide discusses just this manouvre in carrying out a forced landing. Sadly, if the notes had have been worded slightly differently e.g. not recommended for normal operations, it just might have prevented a student overshooting in a forced landing and getting horribly burnt in the ensuing crash (VH-RFW near what is now Jandakot, 1960).
Back to flick manouvres in a Chipmunk - I'm with you mate!
I think we're singing from the same hymn book here!
As I said, the RAF Pilot's Note are delightfully vague, whereas the AFM (now the "last word") simply lists permitted manouvres.
At the risk of digressing (Who? Me?), I'm always intrigued how items appeared in club handling notes and how they eventually become set in concrete, yet no-one can tell you why. I started in Chipmunks in the early 1960's, the club notes specifically banned side-slips with full flap. It was simply verboten without qualification, and God help you if you even thought of doing this. Querying this, I was given a variety of frightening reasons (the aircraft would flick into a vicious spin/the flaps would fall off etc), yet there is no such prohibition in either the AFM or RAF Pilot's Notes. Indeed the Study Guide discusses just this manouvre in carrying out a forced landing. Sadly, if the notes had have been worded slightly differently e.g. not recommended for normal operations, it just might have prevented a student overshooting in a forced landing and getting horribly burnt in the ensuing crash (VH-RFW near what is now Jandakot, 1960).
Back to flick manouvres in a Chipmunk - I'm with you mate!