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TheGreenGoblin
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Spinning...

#1 Post by TheGreenGoblin » Thu Jan 02, 2020 1:03 pm

Not the bicycle exercise class type thing but following on from this very interesting outbreak on the Boeing thread...

https://www.ops-normal.org/viewtopic.ph ... 99#p209799

Really good review of the multiple forces relevant in the spin... (uses jet aircraft as the basis but the content is generic enough to be useful for a better understanding of spin dynamics whatever the aircraft)

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Re: Spinning...

#2 Post by TheGreenGoblin » Thu Jan 02, 2020 1:15 pm

Here a test pilot makes it look easy to spin and recover the PA-38 (Piper Tomahawk aka the Traumahawk) to order...



The Tomahawk is easy to spin (unlike the PA28) but can be very wayward and fickle if the wrong spin recovery technique is used...

Comments on the PA38 spin characteristics..

If anybody here has spun the PA38 they will remember the slightly disconcerting sound of the tail creaking from time to time in the spin. A fun aircraft and a good all round trainer.
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Re: Spinning...

#3 Post by boing » Fri Jan 03, 2020 12:09 am

GG

A stable spin is a balance of inertial and aerodynamic forces hence the weight distribution on the aircraft is important. Jets tend to have, among other considerations such as wing mounted weaponry, relatively shorter wings which changes the crosswise weight distribution because of fuel distribution in the wings. Piston engines are usually mounted ahead of the cockpit so the weight is forward whereas jet engines are mounted behind the cockpit (and so is internal weaponry) so the weight is more aft. Aerodynamically jets have more weight in the fuselage which reduces roll inertia but it makes the pitch inertia greater. Altogether the projection of the spin characteristics of any aircraft is a very complex matter which is still best left to test-pilots.

Example. The Jet Provost 3s and 4s had wingtip fuel tanks, the Mk. 5 did not. You were not allowed to spin a Jet Provost 3 or 4 with fuel in the tip-tanks because it caused the increase in roll inertia to make recovery difficult. The Mk.5 could be spun without this consideration because it had no tip-tanks. Now, the Strikemaster is basically a Mk.5 with bigger engine and tip-tanks. Unfortunately, as one pilot who was not thinking too clearly, found out, the Strikemaster had the same restriction as the Mk.3 and Mk.4. Result one smoky hole and a double ejection.

And just to complicate the situation you have to take gyroscopic precession into account as you consider the inertial forces because you are rolling and yawing at the same time so these forces apply 90 degrees out from where you would expect.

Always made my brain hurt it did!!!!


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Re: Spinning...

#4 Post by Slasher » Fri Jan 03, 2020 2:12 am

I’ve spun the 320 sim and of course the DH82 and Cub. Would’ve like to‘ve spun the 727-200 sim but back then it probly would’ve broken the damn thing. Same with the Dizzy 9-30.

I once flew in a Traumahawk for a one-off Oz CIR renewal but its T-tail to me looked too bloody weak to try anything fancy.

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Re: Spinning...

#5 Post by TheGreenGoblin » Fri Jan 03, 2020 7:52 am

boing wrote:
Fri Jan 03, 2020 12:09 am

Always made my brain hurt it did!!!!
Boing thanks for that detailed and very interesting reply. Trying to visualize the inertial axis and the effects of gyroscopic precession usually turns my brain into mulch. That video and your lucid explanation made visualizing the forces much easier.

As you probably know they don't teach spinning as part of the UK PPL anymore as more people were being killed learning to spin than were being saved from inadvertent spins. They focus on spin avoidance now. I finally learned to spin when I applied for a licence endorsement elsewhere and was taught spinning in the Rheims Cessna.

The guy who taught me insisted we try spinning two other types in order to note the type differences and he also focussed on the effects of weight and balance. Thus I got to spin the Tomahawk and the PA28 -140. The Cessna was really easy to spin and would recover hands off if you didn't apply any into spin aileron. The Tomahawk was interesting because if you applied the correct technique the rate of spin would increase before it recovered. Most disconcerting. It would not recover if you didn"t neutralise the ailerons. The PA28 steadfastly refused to spin and generally would enter a spiral dive.

I tend not to take spinning lightly having lost two flight instructor friends were who killed having got into a flat spin situation.

@Slash despite the creaking I don't recall hearing of any aircraft losses due to the T tail breaking.
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Re: Spinning...

#6 Post by Slasher » Fri Jan 03, 2020 8:07 am

I don’t trust tin that looks fragile Gob! ;)))

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Re: Spinning...

#7 Post by boing » Fri Jan 03, 2020 4:49 pm

GG

I had a very edifying spin session on one occasion which taught me how very close was the line between a successful recovery and ejection. It is all very well entering a spin from the classic "slow her down in level flight then give her a boot of rudder just before the stall" technique and a the immense confusion caused by intentionally entering the spin from an inverted position carrying a few extra knots. There is absolutely no similarity between the aircraft's reaction to the two different circumstances.

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Re: Spinning...

#8 Post by TheGreenGoblin » Fri Jan 03, 2020 6:57 pm

Looking at this video of a SEPECAT Jaguar spinning (and clearly having flamed out gushing unburned fuel vapour) posted by Fox3 which prompted this thread, I can only say that some aircraft and spin regimes are clearly best left to test pilots with ejector seats...




An inverted spin in a high performance fighter jet is clearly not a comfortable or trifling position to be in as this wind tunnel experiment demonstrates (at no risk to anybody's hairdo)....

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Re: Spinning...

#9 Post by boing » Fri Jan 03, 2020 7:06 pm

In the second video you can clearly see the leading edge devices deploying and retracting automatically. God knows what that would do to the recovery, one thing you can be sure of is that whatever recovery action you took could be immediately nullified by the leaders popping out.

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Re: Spinning...

#10 Post by TheGreenGoblin » Tue Jan 07, 2020 1:17 am

How it can all go wrong. Particularly when you have just converted from one specific type to another.

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Re: Spinning...

#11 Post by Slasher » Tue Jan 07, 2020 2:02 am

I read somewhere that the 109Bf had autoslats which operated individually. If one side popped out too early during a steep turn it would fall out of the sky like a bag of sh!t.

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Re: Spinning...

#12 Post by boing » Tue Jan 07, 2020 4:07 am

GG

The accident report is quite correct in its comments on the handling and operation of the aircraft, I would say the report is impressively thorough. No point in complicating the issue with such an excellent assessment but I can imagine exactly what happened simply because we trained students for exactly these eventualities.

Slash,
Don't you remember locking the slats on the Tiger Moth?


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Re: Spinning...

#13 Post by TheGreenGoblin » Tue Jan 07, 2020 11:47 am

Slasher wrote:
Tue Jan 07, 2020 2:02 am
I read somewhere that the 109Bf had autoslats which operated individually. If one side popped out too early during a steep turn it would fall out of the sky like a bag of sh!t.
Some interesting stuff on the 109Bf slats here.

Bf109 leading edge slats....

I always wondered if Mark Hannah had fallen foul of the Buchon's slats in his fatal crash...

https://aviation-safety.net/wikibase/18874
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Re: Spinning...

#14 Post by Slasher » Tue Jan 07, 2020 11:52 am

To boing and Gob: yes the Tiger had the slats lock and an integral part of the checklist. Of the 109 I don’t know but I’ll check Gob’s link a bit later. I need a snooze now before work.

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Re: Spinning...

#15 Post by Fliegenmong » Fri Jan 10, 2020 7:52 am

I learnt spinning in one of these...

https://www.google.com/search?q=A582+Dr ... UgsozqEtgM:

An A582 Drifter, A fabulous aircraft if you like stick & rudder flying! :)

I'd read the stuff, understood the aerodynamics of it, plenty of stall prctice beforehand, passed the theory test, studied the technique etc. .....But nothing prepared me for that first spin, when the shoulder harnesses actually come into play as you peer over the windscreen, and watch the Earth below begin to auto rotate.

Ohh! Look! I found a guy spinning a Drifter on You Yube!, goodness me they were a lot of fun to fly!!



We never let them get past the first spin though...
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Re: Spinning...

#16 Post by Slasher » Fri Jan 10, 2020 8:45 am

TheGreenGoblin wrote:
Tue Jan 07, 2020 11:47 am
Some interesting stuff on the 109Bf slats here.
That was a bloody good read Gob! Thanks indeedy. In particular I liked the descriptions from pilots who actually flew the thing esp in combat. :)

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Re: Spinning...

#17 Post by Fliegenmong » Fri Jan 10, 2020 11:01 am

They set me free SOLO (not 'in', but rather 'on') the Drifter at 11.5 hours...school record at the time! :-bd
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Re: Spinning...

#18 Post by TheGreenGoblin » Fri Jan 10, 2020 5:22 pm

Slasher wrote:
Fri Jan 10, 2020 8:45 am
TheGreenGoblin wrote:
Tue Jan 07, 2020 11:47 am
Some interesting stuff on the 109Bf slats here.
That was a bloody good read Gob! Thanks indeedy. In particular I liked the descriptions from pilots who actually flew the thing esp in combat. :)
Glad you did Captain Slasher. I suspected you would. :-bd

I was a little sad to see that one of the pilots that opined there ref. the Bf109 was poor old Mark Hanna!
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Re: Spinning...

#19 Post by TheGreenGoblin » Fri Jan 10, 2020 5:59 pm

Fliegenmong wrote:
Fri Jan 10, 2020 7:52 am
I learnt spinning in one of these...

https://www.google.com/search?q=A582+Dr ... UgsozqEtgM:

An A582 Drifter, A fabulous aircraft if you like stick & rudder flying! :)

I'd read the stuff, understood the aerodynamics of it, plenty of stall prctice beforehand, passed the theory test, studied the technique etc. .....But nothing prepared me for that first spin, when the shoulder harnesses actually come into play as you peer over the windscreen, and watch the Earth below begin to auto rotate.

Ohh! Look! I found a guy spinning a Drifter on You Yube!, goodness me they were a lot of fun to fly!!

We never let them get past the first spin though...
I imagine that the high aspect ratio of a glider wing would allow quite a bit of rational inertia to build up although being very very light, nothing that an effective rudder couldn't stop with a heavy boot in the requisite direction I guess.

The best aero's I have ever seen were performed by a glider at low level at the Farnborough Air Show. The energy management and skill of the pilot was awesome.

This guy is superb...

Though you remain
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"To be alive
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Your destination remains
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