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Spinning an Airliner

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Spinning an Airliner

Old 16th May 2006, 22:59
  #1 (permalink)  
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Spinning an Airliner

Just wondered if it was possible, say a Dash 8 or 737

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Old 16th May 2006, 23:49
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I would worry more about whether or not it could be recovered from the spin if you did succeed.
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Old 17th May 2006, 01:22
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I'm sure it's possible. Not sure I'd want to be in it when it happened however.
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Old 17th May 2006, 01:23
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Tragically it's been proven to be possible in the 707, as some RAAF aircrew found a number of years ago during asymmetric practice (RIP gentlemen, you're still missed).
That topic's been well discussed so I don't want to open it up again, but yes, at least some types will spin.
As with any machine, the weight distribution, configuration, power settings, speed and so on must influence a type's propensity to spin.

Last edited by Arm out the window; 17th May 2006 at 10:37.
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Old 17th May 2006, 10:56
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Spinning airliners

Sure - I reckon the usual laws of aerodynamics aren't that corrupted or negated by scale, so if you can get to a sufficiently high angle of attack, and you can overcome the natural directional stability, it'll spin. A Dash 8 was lost a few years ago in south west UK, spinning following loss of control during a Vmca check on an air test - like the 707 above. My guess is the only reason it doesn't happen very often is that airliners spend much less of their time at low speed/high AOA than military jets, and very little time indeed in being manoeuvred under those conditions. Also, depending on the CG position, control power may be limited, making it difficult to get to a stall AOA without applying forces and stick displacements that are markedly different from those seen in normal operation.
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Old 18th May 2006, 10:51
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Playing around with Vmca is bound to lead to trouble eventually. An RAAF Hercules in 1960 did a three turn spin before recovery following a Vmca situation during dual conversion. The aircraft was badly damgaged and almost a write-off and in fact Lockheed were interested in exactly what spin recovery action the pilot took as there has been previous spin accidents in Hercs and the aircraft failed to recover. There have been numerous cases of light twins going into a spin during Vmca "demonstrations" - or should we say cock-ups.
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Old 18th May 2006, 23:14
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Lockheed P-3 departure


There is a departure recovery procedure in the NATOPS manual - so it must have been tested.

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Old 19th May 2006, 01:21
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Grrr I bet

I bet Tex Johnston could do it. I know Bob Hoover could. Probably without spilling his tea, either. (R-click 'n save to see why I hold these beliefs...)
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Old 19th May 2006, 02:49
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I bet too!

That most mediums to heavies would break and toss off engines early into a developing spin.
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Old 20th May 2006, 11:18
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I suppose it's quite possible...

Never really thought about spinning a big airplane, but I'm sure it's possible. All you need is a stall in uncoordinated flight, and it'll happen.

The problem with multi-engine airplanes is when you're one engine inoperative...and a stall occurs. If under given conditions, a stall occurs before Vmca (i.e. the stall speed is greater than Vmca), the wings will stall before the aircraft uncontrollably rolls. (This assumes the flying pilot manipulates the controls in a proper manner and maintains coordinated flight.)

Conversely, if Vmca is greater than the stall speed (under the given set of conditons), the plane will roll before the wings stall.

In either of the two above situations, you'll not spin. It's when the two speeds are close to or equal...that's when you soil your panties. She rolls uncontrollably (you're in uncoordinated flight), and the wing (or wings) stall. Yep, you'll get a spin.

So, in Vmca demonstrations, you need to see what speed you'll stall at and then be careful about power/speed combinations to make sure she doesn't roll at or near that stall speed.

Many of the test pilots have the advantage of chutes to assist in stall/spin recovery. As we all know, during training and check rides, many unrecoverable spins inadvertantly occur. What a shame...

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Old 21st May 2006, 01:19
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Not exactly an airliner, but an exec twin that failed to make the UK register - the Mitsubishi MU-2. I was investigating stalling speeds in various configs after some lower than scheduled speeds were found on a C of A airtest, and carried out several airtests after ground checks and engine / airframe adjustments. Finally everything seemingly possible had been checked and a/c should have been perfect. On the next airtest the aircraft auto-rotated at the stall (power off & clean) despite immediate full opposite rudder. The spin developed fully and showed no sign of recovery using 'standard' techniques. There wasn't too much time available as entry to the 'stall' had been 5000ft amsl (normally sufficient as recovery usually only lost a few hundred feet at most) and ROD was off the clock estimated 6000fpm.
I could write a chapter on the next 20 seconds but I'll be brief. After trying in/out-spin aileron (spoilers on MU-2) unsuccessfully, time was running out fast and, in desperation almost, I smoothly increased to max power on the in-spin engine. After about 5 seconds of oscillatory spin the a/c flicked into a spin in the opposite direction which I arrested after about 1/2 to 3/4 of a turn. Resumed symmetric power after closing both levers and recovered at 1000ft above the sea.
Not an experience I'd like to repeat - fortunately I was pretty recent on spinning, having completed 2 years with the Rothman's Team about a year before, my specialist solo manoeuvre being the lomcevak.
Training spins are usually entered by applying pro-spin rudder from level flight (or from manoeuvre) - this one went unprovoked and with corrective inputs. Later extensive investigation revealed an engine problem that caused a slow insidious loss of power on one power plant with no cockpit indications. It would take too long to explain the MU-2's controls and aerodynamics, but the effect of this power loss was, on a 'trimmed' a/c, to reduce the stalling speed by about 7kts and set up all the conditions required for a spin.
Lessons? 1. The UK CAA were absolutely right in not certifying the type and 2. I was wrong, with hindsight, to fly to the actual stall (less than scheduled) - better to stop the exercise at Vs and report 'no stall'. 3. Not a good idea to have a fleet of 1 odd-ball aircraft. If there'd been another similar type in West Africa we could have compared flight characteristics.
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Old 21st May 2006, 09:48
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Originally Posted by Crashking
I bet Tex Johnston could do it. I know Bob Hoover could. Probably without spilling his tea, either. (R-click 'n save to see why I hold these beliefs...)

Great clips, and very impressive, I believe he could too.
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Old 21st May 2006, 14:57
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Hoover's flying is superb, and the reason his show is so impressive (without being terrifying) is that it is sooooo smooth - He knows his survival depends on keeping the airplane in the regime where airplane/control response is approximately linear. I believe the only airplane he spun in shows was the NAA F-86 Sabre.

As well-thought-out is the dead-stick Shrike Commander routine, his P-51 show closer (touchdown on the numbers - pullup and roll - land & stop on the remaining runway) is REALLY convincing.
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Old 21st May 2006, 15:21
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Spinning A340

I've heard that if you disonnect enough of the Protection Factors in an A340 sim that it does quite an impressive spin. Not sure about the real a/c.
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Old 21st May 2006, 16:35
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Originally Posted by DIVESAILFLY
I've heard that if you disonnect enough of the Protection Factors in an A340 sim that it does quite an impressive spin. Not sure about the real a/c.
Does the simulation include failing the engine pylons due to centrifugal G's?
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Old 21st May 2006, 17:01
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I'm with you there barit1. I wouldn't say anything to detract from the excellence of Bob Hoover or Tex Johnston, but rolling and spinning cannot be compared. I doubt if either of these 'aces' would have been stupid enough to consider a deliberate spin in a 707. A well executed barrel roll is harmless to an aircraft (though if screwed-up one of the greatest height losers - Bullock (RIP) A26 Biggin Hill), but a spin has many other forces (centrepetal, sideslip etc) and I seem to remember early 707s were quite prone to shedding pods with quite small amounts of sideslip.
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Old 21st May 2006, 18:07
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Originally Posted by DIVESAILFLY
I've heard that if you disonnect enough of the Protection Factors in an A340 sim that it does quite an impressive spin. Not sure about the real a/c.
Barit + Rod, agreed.
One of the 320 sims we use does an impressive manoeuvre if you apply standard spin initiation, but I would call it a spiral dive rather than a spin. That might be because of the physical restraints of the jacks.
We learn a lot from sims eg: 'would the REAL aircraft do that?'. Usually the answer is 'yes'.
Not, I fancy, in the case of spinning.
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Old 21st May 2006, 21:35
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I would be utterly astonished if any commercial aircraft simulator had an accurate representation of the aerodynamic forces and moments in an actual spin, given the almost total absence of any data whatsoever on which to based the modelling. It's a flight regime where little or nothing can be extrapolated to from normal linear aerodynamics, and to actually build a realistic spinning aerodynamic mathematical model is not a trivial task by any stretch of the imagination. (When I was at BAe we had post-stall/spin models for the Hawk, but I don't think any of us would have considered them other than a general representation of the aircraft's behaviour, and that was WITH the benefit of large amounts of flight and wind tunnel data to base the models on)
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Old 22nd May 2006, 11:57
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Got me thinking about this one now. My immediate reaction was agreement to the statement about engines falling off if a big jet did spin, but then I thought about it some more. First, the rotation rates are probably going to be lower - big inertias to overcome with aerodynamic forces. Second, IAS will be low - the average airliner doesn't have fighter power to weight ratios and will almost invariably be at low speed at spin entry, either because the pilot stuffed up some low speed handling (e.g. Vmca) or generated more drag than thrust in the manoeuvre leading to the stall. The structural loads are dependant on dynamic pressure, i.e. square of IAS. The average airliner is designed to cope with, for example, an engine failure at max IAS that generates significant sideslip by the time the usual allowances for yawing moment due to asymmetric thrust, directional stability, and for the average pilot to react to same and apply corrective control have all been applied. The resulting structural forces would have to be pretty significant compared to those generated at the low speeds seen in a spin, even allowing for the higher sideslip angles, because they're proprotional to the square of the speed.
That said, the above relates best to airliners with jet engines: I reckon the gyroscopic effects on big propellors would be way more whacky, so I'd tend to agree with the earlier assertion about losing engines if you want to go spinning a C-130 or P-3.
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Old 22nd May 2006, 13:39
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Ref Fantoms post, allegedly some Arse tried the same manoeuvre in a B777 sim and the box attempted to launch itself off the jacks and into the coffee shop next door. Left , right , left , right, hats off interview with no tea and bickies.
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