L-29 crash at Argentine Airshow 12/11/23
 

Another low pass and roll goes wrong...

https://aviation-safety.net/wikibase/347812

The L29 seems to have suffered quite a few accidents over the years in civilian use.
Suffering the same fate as the Hunter perhaps. Fast ship in the wrong hands?

Pilots have very likely missed or failed to compute the "enegy gates" to execute the maneuver. I dont know what they intended to do, if it was a barrel roll ( probably not as they interrupted it while inverted unless they were disoriented or incapacitated) or more likely a reverse cuban 8 ( Pull to 45 degrees up pause then pull through then level off) .

For a normal roll even with the "pause" while inverted would have been a non event, they would have ended up upright though nose low with plenty of height available, they had plenty of energy available after that high speed low pass.

But -and here lies the risk- with this same energy to spare on the reverse cuban 8 after inverted the "energy gate" was busted: way too low and fast. Closing that portion of the loop while inverted was impossible, the radius arc ( It increases at the square of the velocity, double the speed quadruple the radius) was too large and there was not enough room to allow for it other than stall under g while pulling to avoid hitting the ground.

When "energy gates" are not considered in advance, any non compliance or improvisation is a big risk, then the maneuver should be aborted; From inverted complete the half roll and recover straight and level. You may well have luck in a light aerobatic Extra aircraft with his quick roll rate and ligher wing loading, but no chance on a heavy underpowered military jet trainer.

The laws of physics are non negotiable. Speed and height did not permit that closure of the maneuver. It should have been aborted.

There is a similar, very similar incident of an italian eurofighter which hit the sea in the same fashion,in Pratica di Mare some years ago, just google for it.

It was much higher that this L29 probably in excess of 10'000 feet but with much higher closing speed it 3-400 knots I would assume, the radius to close the maneuver was immense, and while pulling out agressively with the sea appraching the Eurofighter stalled under heavy G and pancaked, The L29 likewise stalled dropped a wing and flipped.

More than" fast ship in the wrong hands", fast ship without proper training and improvisation.

that is a bit odd. The control authority is there at all times, they convert a simple upward vector aileron roll into a.... whatever that was. The attitude was never high enough to consider doing a half roll and pull through reversal, part of a cuban, but, then they drop the nose and run out of ideas. The last video segment suggests there may have been a very late short duration stall or it was hesitation by the pilot who was seeing the planet coming up quickly in his windshield. Assuming the pilot had any competency in aerobatics, it is a strange flight path. It isn't G-LOC, and if there was an aileron restriction early on while inverted, that cleared prior to impact, so seems odd, unless a harness/control interference may have occurred. Sad outcome.

Wouldn't say it's odd, rather just another in a sad litany of low passes and rolls that have seen the nose drop while inverted followed by an unintentional dive with no way out. Most notorious I can recall is the Biggin Hill Invader in 1980.

Hurricane at Shoreham being another.

Hunter?

The hunter was a slightly different situation, being an unrecovered loop, rather than roll, but similar theme....

DAR, DT2 is referring to a Hurricane crash at the show in 2007, there used to be a video of the event but all I can find now is post crash, occurred during a mock dog fight with a few other participants.


Accident report extract.

I was present at the Hurricane accident but didn't see it, but the video clip I saw looked nearly identical to the Firefly crash at Duxford which I did witness. Both aircraft were being flown fairly conservatively.

I used to feel a bit uneasy watching one pilot loop a vintage fighter apparently somewhat slower than Ray Hanna, Brian Smith, et al tended to do. I'm sure he had speed in hand and probably his mostly flatter displays didn't require quite as much energy management as the other exponents did but it still made me look away. Glad to say he and his aeroplanes are still with us, though he no longer flies displays.

Fair enough, another low level aerobatic crash I did not know about!

Now we are at it, there was a similar SAAB Gripen crash in Thailand a few years ago.

You could also add the Duxford P38 crash although that one goes firmly in the `unexplained` category. Outcome the same.

There was yet another similar looking crash of a T28 in Hungary earlier this year.

The deadliest airshow crash of all time, 77 killed, including 28 children, 543 injured, 100 0f whom were hospitalised, the two pilots survived with minor injuries.

Megan correct me if I'm wrong but did North America and Europe establish more stringent rules regarding no flight paths directly over the crowds.

The pilots stated that the airbase map they had received differed from the actual layout they found at Sknyliv airfield, where they had been also denied an extra rehearsal flight before the show for financial reasons. Although the root cause of the crash was found into the pilots violating the plan and performing “difficult maneuvers they had not done before”, other factors, including a small flying zone and inappropriate zoning by the show organizers who had allowed spectators to gather so close to the flight line were blamed for the tragedy.

The court found the two pilots and three other military officials guilty of failing to follow orders, negligence, and violating flight rules. Two of the three officials were sentenced to up to six years in prison; the third received up to four years, a military court sentenced pilot Volodymyr Toponar and co-pilot Yuriy Yegorov to fourteen and eight years in prison, respectively.

I think the Frecce Tricolari crash at Ramstein tightened up a lot of rules regarding overflights of or manoeuvres towards crowd lines. As far as I know, the Red Arrows still start their display with an overflight from behind the crowd but at 500' or whatever. I recall a foreign Jungmann flying in towards the crowd at a display and pulling up into a stall turn well inside the safety line, commentator Brendan O'Brien saying something like "please don't do that there...". Believe it was the same pilot who died flying the same aircraft during a display in France the following weekend.

The Biggin Hill Invader crash (pilot plus six passengers) triggered a ban on passengers being carried at air displays - nevertheless I've seen two back seaters die in subsequent accidents whose presence may not have been necessary.

Maybe it would be the right thing to think about what these displays are good for? Showing off by individuals? Scare the crowds? Get spectacular pictures for marketing or news? Show aircraft outside of their normal envelope?
These mostly are veteran aircraft and sometimes veteran pilots, some not with military background and not current like say flight instructors on type. The airframes can be old and fatigued and engines limited or just too precious to risk crashing (well, not an L-29).
From my point of view it would be wiser to limit displays to more moderate manoeuvres like takeoff and landings low flybys fast and slow and some moderate turns. Even during their day many military types had their limits and risks why trigger extreme manoeuvres today when the same frames are worn out and old? Look how Shuttleworth's Edwardians got so old.
Without wanting to spoil the fun but with so many historic aircraft crashing and lost I'd prefer a more moderate style. This should be made a regulation. If not by the authorities then by the insurers. I know somebody privately owning (and keeping) a Mustang and what kind of training and experience the insurance requires before a single pattern.

What examples are there of old aircraft crashing because they are old or 'worn out'? The most common single factor appears to be misjudgement of speed and/or altitude at low level, and this can happen to current military pilots as much as anyone else. EG The Mountain Home Thunderbirds crash.

The Swiss Ju 52 comes to my mind. It could not out climb a mountain valley under hot and high conditions. The wreck revealed serious structural aging that had gone unnoticed before.

... but which had nothing to do with the crash. Also, that was an airframe that was still used commercially (in a sense) and therefore had a very different usage background than a typical warbird.

In 40 years of going to airshows and being aware of the accidents that have happened I've never heard of a fatal accident to a warbird caused by fatigue. Pilot error, poor maintenance occasional engine failure yes. The only fatigue I can remember was a ww1 replica so a modern aircraft.

There is a wiki list not of airshows but structural failures in general. My point was better don't stress old aircraft with extreme maneuvering.
https://en.wikipedia.org/wiki/List_o...tural_failures

And Airshow crashes:
https://en.wikipedia.org/wiki/List_o...e_20th_century

That is a very unhelpful list... structural failure is a side effect of an airframe breaking up, but it's the reason for the airframe breaking up that is the pertinent issue in an accident investigation. That list contains everything from design issues to mis-handling of a manoeuvre and everything in between. You cannot draw any conclusions from that.

'Don't stress old aircraft' appears to be a good point, but I think it should be phrased slight differently: 'don't over-stress old aircraft'. Any airworthy airframe is more than capable of handling normal stresses. There are loads of manoeuvres that can be carried out safely by any airworthy craft. Actually, the phrase should be 'don't over-stress any aircraft'.

We shouldn't be discussing this, we should await the results from the accident investigation and start from that. It is way too soon to come to any conclusions on what we should or should not do based on this particular accident.

It had not "aged", it had corroded due to shoddy maintenance. The accident report basically found that the operator for years had done everything wrong; maintenance, flying standards, everything that they could possibly ignore, neglect and/or do wrong they did...

Apart from maintenance done wrong, wreck parts from the inside of the structure, normally inaccessible, were analyzed and found to be badly corroded and fatigued.

If you mean the Hoof Proudfoot crash he was wearing a kneeboard that we believe interfered with the yoke during the backside roll recovery.
Kneeboards are a VERY bad idea when mixed with level 1 aerobatics.....ESPECIALLY with a yoke involved as is the case in the 38.
Dudley Henriques

Slightly off topic but wasn't there an ex Battle of Britain (or maybe just a display) pilot who used to stall roll the Spitfire?

Do you mean flick roll? Bob Stanford Tuck certainly included it in his wartime repertoir, from memory at something like 100-120kts.

Always fascinated by the Zlins 526s etc which almost seemed to take a deep breath as flick inputs are applied. Extras and the like are so twinkle quick it's hard to say what happened.

Edit: got a feeling I've heard that Tony Bianchi performed an Aresti sequence in Patrick Lindsay's Mk1 back in the '70s probably at Booker. Whether he included a flick I know not.

Maybe flick roll is the term. I was told you stall one wing and then convert it into a (flick?) roll or something like that.

It's really nothing more than a snap roll, or more accurately an induced spin in the horizontal plane. It's not a maneuver we usually do in WW2 propeller driven fighters but can be done if done carefully and with good stick and rudder skills.
Airspeed is critical as initiated with too much airspeed the aircraft can easily be over g'd.
In the combat sense it would be considered a defensive maneuver used to shake an attacker out of a guns solution and cause an overshoot in the plane of the defender's turn.
Generally however, (I displayed a P51D on occasion) we don't consider flick rolls as a normal display maneuver as it's an energy loss maneuver leaving you with little maneuvering energy to continue on with a display routine.
Dudley Henriques

Dudley, in some 50 years of watching WW2 fighters displayed, I've certainly never seen one snap/flick rolled!

The first flick roll I can recall seeing was probably Neil Williams in Aerobatics International's other Pitts (think 'ZPH had a broken longeron at the time and was rebuilt with a new fuselage), might have been Mike Riley or James Black, but Williams was certainly there and flying. Second aircraft I saw flick rolled was a Chipmunk at the same show. Only warbird I've ever seen flick rolled was a Harvard performing a nicely flown avalanche quite recently.

When it comes to snap rolls the Harvard or AT6 as we call them here in the states is an exception .he Harvard does a beautiful snap roll due to the wing sweep outer leading edges on the wings. We snap the old T6 all day long. In fact, I've displayed the T6G in airshow displays and snapped it myself.
WW2 fighters on the other hand are a different story. They can of course be snapped and the "flick roll" as done on the Spitfire can attest, but generally speaking, we don't "snap" these aircraft as a general rule.
A normal display routine for a WW2 fighter during an airshow is performed within an envelope within +5g and -1g. In the case of the Mustang there is a negative g limit due to oil pressure loss. Generally true for other WW2 era fighters as well.
Dudley Henriques

Some where in the library there is a story written by a WWII Spitfire pilot, who having trouble with an enemy on his tail, basically flick rolled the aircraft into a spin, one wing was so twisted by the exercise that the slowest he was able to fly was some 150 knots, wing being so twisted that he ran out of aileron control.

An accidental flick into a spin was said to be some thing that saved inexperienced P-51 pilots when pulling a tight turn to evade the enemy behind.

In combat you do what you have to do. Generally speaking when defensive a "flick roll" could be a last ditch maneuver to force a shooter into an overshoot.
The airspeed at which a "flick roll is initiated" is critical. Too fast and you can easily over g the airplane. So slowing it down to where you can safety "snap it" is the key.
Because ANY snap roll in ANY airlane is an energy loss maneuver, doing one in combat should be considered a "desperation" maneuver, not something you would wnat in your normal "bag of tricks" as a combat pilot.
Dudley Henriques

What a priviliege and a pleaseure to have such an authority as Mr Henriques posting in this forum, I advise all of you to get acquainted with him via google and read his many artcicles and posts.
He his one of the last "Gurus" of aviators and pilots with such an experience, knowldege and narraitive. Welcome

Here's what Bob Tuck had to say about flick rolling a Spitfire, as recounted to Larry Forrester in Fly for your Life:

As an American fairly familiar with flying WW2 fighters I would say without hesitation that were I to go up on a display that included "flick rolls" I would choose as my mount to do that a Spitfire over all other planes of choice, preferably a clean Mk 9 or earlier. Mitchell designed the perfect fighter for the BOB mission. Granted it was the Hurri's that bore the brunt of the battle but the Spit was indeed something else when it boiled down to a good old fashioned dogfight.
I never got to meet Tuck but Bader and I were friends for years. I also got to know Winkle fairly well and we had a wonderful time trading letters back and forth where he would go on and on about the high Mach dive testing they did after the war. Douglas was no slouch when it came to arguing a point and we would go at it tooth and nail comparing my Mustang and his Spitfire. LOL. Douglas mentioned doing "flick rolls" in the Spit, usually at reduced gross weight and at low airspeed. He agreed with me that the 51 was a bit heavy even at 1/2 fuel to be doing snap rolls. It was easy to load up a 51 with excessive pitch rate. I have to admit I never actually tried to do a snap in the Mustang. It was considerably heavier than a Spitfire and carried a lot more fuel.
I will say also that some of the finest pilots I have ever known were friends from Great Britain. What they did during the BOB in my opinion has never been equaled in the annals of aerial combat.
RIP Douglas and Eric. I truly miss you both very much.
Dudley Henriques

I have questions: What is/is there a difference between a flick roll" and a "snap roll"? I understand a snap roll to be a spin on a horizontal axis (essentially, the inertia of the airplane carries it along the horizontal path long enough to enter and recover a one turn spin along a horizontal axis - which I have been taught is a snap roll). Was I taught correctly? The forgoing description make the flick roll also sound like a well recovered horizontal spin to me....