Garfly Posted January 24 Posted January 24 Spin Training - Deadlier than Not? BLOG.COMMUNITYAVIATION.COM Rich Stowell's specialty has always been spin, emergency maneuver, and aerobatic training. He doesn't provide primary flight instruction but has seen the result of our flight training system in pilots who have... https://www.communityaviation.com/hubfs/Rich Stowell/Blog/Post 004 Spin Training Myth/Link 3 - 12 Stall Spin Myths with Bonus Myth.pdf 2 2
BrendAn Posted January 24 Posted January 24 6 hours ago, facthunter said: NO disagreement with anything there.. Nev would you intentionally put a jabiru into a spin with such a small rudder. i mean in a training situation if it were allowed.
facthunter Posted January 24 Posted January 24 IF it's allowed it would be certified or tested. There's more than the size of the rudder that matters. There was a lot of contention about DHC-1 Chipmunks spin recovery predictability and I was NEVER fully sure of how it would recover so allowed plenty of extra height like other s did. Nev 1 1 1
F10 Posted February 7 Posted February 7 On 24/01/2024 at 8:46 PM, BrendAn said: would you intentionally put a jabiru into a spin with such a small rudder. i mean in a training situation if it were allowed. The rudder hastens recovery, but it is I think, not the main factor here. Un-stalling the wings, aileron neutral, is vital. Un-stall the wings and the aircraft has no option but to fly again, recovery resulting in a steep dive angle. Damping in roll will stop the rolling, directional stability will stop the yaw in the resulting dive. As I've said, most aircraft should recover when holding controls neutral. The inertia in the yawing plane is large, so opposite rudder hastens the recovery, but I don't think as important as unstalling the wings. One important phenomenon occurs here. The outer wing will un-stall first in a spin recovery. This results in a rapid short term increase in roll into the spin. To some it may appear the spin is getting worse, but it is in fact a sign of recovery. 1
facthunter Posted February 7 Posted February 7 A shielded or too small a rudder will jeopardise the recovery in my view (and that of many others.) The first recovery action after close throttle IS is full opposite rudder. In some planes moving the stick forward shields the bottom of the rudder more. DO WHAT is the technique for YOUR Plane. There's NO ONE answer for all types. IF you end up with FULL FORWARD stick as soon as it unstalls, CENTRALISE the controls or you may end up in an INVERTED SPIN very quickly The airspeed tells you whether your are spinning OR in a Spiral. If it's more or less just above stall speed depending on a few things one of which is the side your Pitot is on and how nose down the spin is.. These days not many get the chance to practice spins , focussing on avoiding them, but some instinctive common Pilot reactions can put the plane into a spin and at circuit height you WON'T recover.. We continue to see examples of this far too often. Nev 1
F10 Posted February 7 Posted February 7 Yes, absolutely, always read your aircrafts spin recovery technique. I was referring to the fact a safe aircraft should recover with controls held neutral. Of course opposite rudder is important but I still say un-stalling the wings is top priority. I was not suggesting ignoring your aircrafts flight manual recovery procedure. Of course fuel loads and CofG position issues can make an aircraft behave very differently in a spin and may make the spin unrecoverable. Yes blanking of the rudder can occur with down elevator, that is why a number of aircraft have “ staggered” empenages, where the fin/rudder is mounted further ahead of the horizontal tailplane, to avoid rudder blanking. Chipmunk, Piston Provost and the Machi jet, are examples. Again most aircraft should recover with the stick getting to slightly forward of neutral. Full forward stick may well be necessary, but I would say not normally required. A consideration of the stick far forward on recovery, can lead to a very low nose on recovery, leading to greater height loss.
LoonyBob Posted February 7 Posted February 7 2 hours ago, F10 said: Yes, absolutely, always read your aircrafts spin recovery technique. I was referring to the fact a safe aircraft should recover with controls held neutral. Of course opposite rudder is important but I still say un-stalling the wings is top priority. I was not suggesting ignoring your aircrafts flight manual recovery procedure. Of course fuel loads and CofG position issues can make an aircraft behave very differently in a spin and may make the spin unrecoverable. Yes blanking of the rudder can occur with down elevator, that is why a number of aircraft have “ staggered” empenages, where the fin/rudder is mounted further ahead of the horizontal tailplane, to avoid rudder blanking. Chipmunk, Piston Provost and the Machi jet, are examples. Again most aircraft should recover with the stick getting to slightly forward of neutral. Full forward stick may well be necessary, but I would say not normally required. A consideration of the stick far forward on recovery, can lead to a very low nose on recovery, leading to greater height loss. In a developed, rather than incipient, spin, the outer wing has unstalled and is driving the spin; this is what "developed" means. The ICAO airworthiness standards for spinnable aircraft were taken to require recovery from three turns of developed spin, but manufacturers pressured Safety Authorities to accept three turns of incipient. The aircraft you neme can all recover from a developed spin. Pushing the nose down tends to increase airspeed, which both helps unstall the in-spin wing, and reduced the VS blanketting from the HS. It also reduces the polar moment of inertia of the fuselage, which reduces the force required to stop spinning. However, like an ice dancer pirouetting and pulling in their arms, the stored rotational inertia causes a short-term increase in rate of rotation. The wing polar moment is the major factor, and masses along the wing - fuel, U/C - make spin recovery much more challenging. NACA's research into spinning twin-engined aircraft (which drew heavily on Luftwaffe experience) was interesting; in most cases, pilots ended up using differential thrust to bring them out, after applying full foward elevator and rudder as suited the specific aircraft. Any aircraft which is to be deliberately spun, requires control surfaces demonstrated to considerably higher speeds, and an airframe to a considerably higher load factor than Utility Category, due to the likelyhood of overspeed and adrenaline-fuelled pullout of the resulting dive. Blaniks are fun to spin, provided those Red Bull loonies have not been at them... 2
Blueadventures Posted February 7 Posted February 7 Blaniks are fun to spin, provided those Red Bull loonies have not been at them... They sure were and fun fly over all. Had a L13-A1 VH-GPS one and miss having it; it’s still flying in NSW. One of the few in the world. 3
LoonyBob Posted February 7 Posted February 7 26 minutes ago, Blueadventures said: Blaniks are fun to spin, provided those Red Bull loonies have not been at them... They sure were and fun fly over all. Had a L13-A1 VH-GPS one and miss having it; it’s still flying in NSW. One of the few in the world. The only L13s not grounded now, have the Transavia /Llewellyn life extension mod. Glad at least one is still being used! 1 1
facthunter Posted February 8 Posted February 8 By moving the Fin and Rudder forward you are reducing it's moment arm and effectiveness The "G" measured in a pullout in My Citabria never exceeded 2.5 G. All parts of the spin are quite nose down. IF you hit a bit of turbulence at the same time that "G"figure will rise substantially. A C-150 at Port Macquarie years ago. Bent the fin over at near 90 degrees when the student didn't centre the rudder during recovery and the speed built up. No one was hurt. Nev
LoonyBob Posted February 8 Posted February 8 10 hours ago, facthunter said: By moving the Fin and Rudder forward you are reducing it's moment arm and effectiveness The "G" measured in a pullout in My Citabria never exceeded 2.5 G. All parts of the spin are quite nose down. IF you hit a bit of turbulence at the same time that "G"figure will rise substantially. A C-150 at Port Macquarie years ago. Bent the fin over at near 90 degrees when the student didn't centre the rudder during recovery and the speed built up. No one was hurt. Nev Your first sentence would be spot on, if the HS was nowhere near the VS. The textbook guidance, based upon 1930's research, is that between a line projected up at 30 degrees aft of vertical from the HS LE at the root, and a line projected up at 60 deg aft of vertical from the HS TE, the dynamic pressure is ~25% of the free stream value, and so HS in this area is ~25% as effective as it should be in stopping a spin. This was a significant incentive to try "T" tails, but they have their own issues... I agree that one should never need to exceed 2.5G, but numerous people have committed their unintentional spins at low level, and the ground tends to encourage avoidance manouvres. The airbatiC has plenty of keel area, so spins quite nicely... a nice aeroplane all round. Blanik (G)VB, when I flew it, tended to drop the nose past 90 degrees when stalled from slow straight-ahead flight, and it took a few turns to get back to a stable-ish ~50deg nosedown. It wasn't really coming down all that fast, but it certainly felt like it! (VP was altogether more gentlemanly...) The Cessna fin spar bulkhead was a steady money-earner for maintenance organisations, so I'm not really surprised... there might have been some shed vorticity at work, too. The F-18 (developmental) had similar issues in a high-G pullout, and I don't think the original F-16 finpost was great shakes either. 1
facthunter Posted February 8 Posted February 8 IF your nose is pointing at the ground and you don't have enough height, it's "game over" anyhow. Nev 2
F10 Posted February 18 Posted February 18 On 7/2/2024 at 11:25 PM, LoonyBob said: In a developed, rather than incipient, spin, the outer wing has unstalled and is driving the spin; this is what "developed" means. The ICAO airworthiness standards for spinnable aircraft were taken to require recovery from three turns of developed spin, but manufacturers pressured Safety Authorities to accept three turns of incipient. The aircraft you neme can all recover from a developed spin. Pushing the nose down tends to increase airspeed, which both helps unstall the in-spin wing, and reduced the VS blanketting from the HS. It also reduces the polar moment of inertia of the fuselage, which reduces the force required to stop spinning. However, like an ice dancer pirouetting and pulling in their arms, the stored rotational inertia causes a short-term increase in rate of rotation. The AP3456A Royal Air Force Manual of Flying defines the spin as having two phases, incipient and fully developed. The difference is in the fully developed spin (after 3-4 turns) the moments of inertia in pitch roll and yaw, have built up so that as Newton One states, the aircraft wants to keep doing what it’s doing. That’s what makes correct recovery action important. In the incipient phase, recovery is almost instant by power off, centralising the controls, (do not use aileron). Yes the outside wing is in a lesser state of stall granted still flying even, so more lift, than the inner wing. If you imagine the rotating mass of the fuselage, a rotating mass has the properties of a gyroscope, and this gyroscopic precession. Replace (the pitching fuselage with a spinning bicycle wheel to prove this). The delta wing has far more yaw than roll in an autorotation. By banking the mirage into the spin, using aileron (match the yellow stripes on the stick with the yellow stripes on the cockpit sills), and in doing so, the roll force applied to the fuselage “gyro”, and this roll is processed through 80 degrees in the direction or rotation (pure gyroscopic law of precession), and becomes a yaw force, yawing the aircraft out the spin. This is the B/A ratio, a heavier fuselage being anti spin rather than a heavier wing. Easy hey!!
facthunter Posted February 19 Posted February 19 I would imagine a DELTA wing would be an entirely different kettle of fish. to a conventional plane. Nev. 1
LoonyBob Posted February 22 Posted February 22 On 18/02/2024 at 5:24 PM, F10 said: The AP3456A Royal Air Force Manual of Flying defines the spin as having two phases, incipient and fully developed. The difference is in the fully developed spin (after 3-4 turns) the moments of inertia in pitch roll and yaw, have built up so that as Newton One states, the aircraft wants to keep doing what it’s doing. That’s what makes correct recovery action important. In the incipient phase, recovery is almost instant by power off, centralising the controls, (do not use aileron). Yes the outside wing is in a lesser state of stall granted still flying even, so more lift, than the inner wing. If you imagine the rotating mass of the fuselage, a rotating mass has the properties of a gyroscope, and this gyroscopic precession. Replace (the pitching fuselage with a spinning bicycle wheel to prove this). The delta wing has far more yaw than roll in an autorotation. By banking the mirage into the spin, using aileron (match the yellow stripes on the stick with the yellow stripes on the cockpit sills), and in doing so, the roll force applied to the fuselage “gyro”, and this roll is processed through 80 degrees in the direction or rotation (pure gyroscopic law of precession), and becomes a yaw force, yawing the aircraft out the spin. This is the B/A ratio, a heavier fuselage being anti spin rather than a heavier wing. Easy hey!! I agree that a Mirage, especially fully fueled, would act a good deal more like a gyroscope than does a cruciform aeroplane; but the Mirage gains its lift pretty much exclusively from vortex lift (forget Prandtl for a moment!), and so cannot experience a local separation of flow normal to the leading edge. It's a different beast in many ways. Precession is a reaction to an imposed torque normal to the axis of rotation, and occurs at 90deg to the applied torque, still in the plane of rotation; in an aeroplane, that would mean that the rudder would produce a pitch reaction, and vise versa. This is seen not to happen in cruciform aeroplanes. Non- Mirage flyers, consider a non-delta aeroplane just after pitch-down. The fuselage major axis is closely aligned to what is about to become the axis of rotation; the wing is almost normal to same. The integral of the squares of the distances of the wing elements from the axis of rotation is enormously greater that those of the fuselage; the wing inertia is considerably more critical, and remains so until the spin flattens. In said inclined state, a lift differential from tip to tip will start to drive a rotation, rather than support the aeroplane, because the lift is near normal to gravity. Correct spin recovery control input for test flying involves STARTING by centralising controls, and then - depending upon the results of a study of the physical details of (at least) the control surfaces, lifting and stabiliser surface geometry, location and execution, and the rear fuselage - either maintaining neutral pitch input and applying anti-spin rudder, or maintaining neutral rudder input & moving the stick smoothly to the full nose-down position. If recovery does not initiate, and height allows, cycling the stick is commonly the next step, followed perhaps by applying in-spin aileron, or cycling the rudder, or various combinations of the above. If the spin continues, one normally recentralises the controls, and (in a small aeroplane) moves the seat to the full-fowards position, possibly removing the harness and getting as far forwards as practicable. At some point, one deploys the (anti) spin 'chute, and then flies back to base, trying to figure out wtf can be changed on the aircraft to make it behave. I understand that when John Thorp (of NSW Region DCA, not the designer bloke) was investigating the unrecovering Chipmunk mystery, he followed very much this routine (I don't know if he had a spin chute fitted, but he didn't deploy one); after spinning the first Chippie, he flew to base and reported that the aircraft was unrecoverable by normal means, and that the fleet was (would remain?) grounded until he had cleared each aircraft. He went on to spin every Chippie on the Australian register, and cleared each and every one with the new stick grip removed and the old one returned to service. Apparently, the conformal grip reduced the stick foward travel by a few mm, which was enough to make the difference. 1 1
djpacro Posted February 23 Posted February 23 23 hours ago, LoonyBob said: I understand that when John Thorp (of NSW Region DCA, not the designer bloke) was investigating the unrecovering Chipmunk mystery, he followed very much this routine (I don't know if he had a spin chute fitted, but he didn't deploy one); after spinning the first Chippie, he flew to base and reported that the aircraft was unrecoverable by normal means, and that the fleet was (would remain?) grounded until he had cleared each aircraft. He went on to spin every Chippie on the Australian register, and cleared each and every one with the new stick grip removed and the old one returned to service. Apparently, the conformal grip reduced the stick foward travel by a few mm, which was enough to make the difference. I don't see any of that in the report? Nowhere do I see a mod to the stick grip however there is mention that harness may restrain positioning of the stick.
LoonyBob Posted March 6 Posted March 6 On 23/02/2024 at 11:14 AM, djpacro said: I don't see any of that in the report? Nowhere do I see a mod to the stick grip however there is mention that harness may restrain positioning of the stick. I'd love to see the report; I had my gossip (much later) from a couple of members of NSW DCA at the time... 1
facthunter Posted March 6 Posted March 6 I did plenty of spinning in the chippee and others and never felt the way it recovered was that reassuring and I've spoken with plenty of top pilots about it since. As far as full forward stick is concerned. One of these pilots of considerable repute said he ended up spinning inverted which does not surprise me. I always allowed an additional margin of height for recovery and prepared myself mentally before doing the spin. I was around when the Plane was assessed in the mid 60's. I felt it passed because we needed it to quite frankly. The size of the rudder was of some concern (too small) for even doing some aerobatics. and a few modified ones existed. Nev 1 1
Area-51 Posted March 7 Posted March 7 Chippy had a shielded rudder; spin recovery results to be expected and not surprising; end of story...
facthunter Posted March 7 Posted March 7 If you examine it carefully the shielding of the rudder by the horizontal stabiliser is much less that a lot of others. Nev 1
djpacro Posted March 9 Posted March 9 On 06/03/2024 at 11:06 PM, LoonyBob said: I'd love to see the report; I had my gossip (much later) from a couple of members of NSW DCA at the time... Try this Collision with terrain involving DHC-1, 'Chipmunk' VH-UPD near Coffs Harbour, NSW on 29 June 2014 | ATSB 2
facthunter Posted March 9 Posted March 9 Most spins not recovered from in this Plane type were fatals as the stabilised RoD is above 6,000 fpm in a spin.. You can see the high energy flat attitude results in the Photo. Deformation in the forward cockpit is extensive. I guess the amount of DHC-1 flying at that time was much less than in the 60s so the grapevine would be non existent.. Nev 1
djpacro Posted March 10 Posted March 10 On 9/3/2024 at 2:20 PM, facthunter said: Most spins not recovered from in this Plane type were fatals as the stabilised RoD is above 6,000 fpm in a spin.. You can see the high energy flat attitude results in the Photo. Deformation in the forward cockpit is extensive. I guess the amount of DHC-1 flying at that time was much less than in the 60s so the grapevine would be non existent.. Nev Someone happened to catch it on video. 1 2
djpacro Posted March 14 Posted March 14 I heard a rumour that Rich Stowell is visiting Australia soon for some seminars and flight training. 3
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