Flat spins

[hoey5o]

Just started flying an ac that has a tendancy to flat spin and
before I have to start looking at it in the air I would appreciate
any info anyone can give or any descent books etc to look at on the theory of it all.
(this maybe should go in flight testing but ah well)

[keithl]

I should say "descent books" are probably the right kind!
Sorry, couldn't resist...

[hoey5o]

oh dear sorry, I think Ive been flying to long.

[Genghis the Engineer]

I'll happily answer here, but will also say as moderator of the "Flight Test" forum that you'll probably get a better answer over there (and I'll forgive you a second post in that forum if you want to leave this here rather than move it).

A flat spin is one where the nose comes up to something approaching the level flight attitude during the spin, often causing a more blanked rudder than would normally be the case. They can be difficult to recover from, occasionally impossible, always disconcerting. Recoveries can occasionally be non-standard, particularly in terms of pitch control since the objective may become to unblank the rudder rather than simply get the nose down - you certainly want to be familiar with the recommended recovery from the POH.

Books, there are many, but the best starting point is Darrol Stinton's "Flying Qualities and Flight Testing of the Aeroplane" whose spinning chapter is long, thorough, and particularly concentrates on piston-singles.

I did post a reading list on Spinning in this thread (http://www.pprune.org/forums/showthread.php?s=&threadid=93744&highlight=Spinning) a while ago which might be worth a look. If you would like to divulge the type also, the odds are that somebody on Pprune has spun it already - possibly even formally investigated the spinning - and can give you some steers from personal experience.

If there's anything in there that you desperately want and can't get hold of, give me a shout and I'll see if I can help out, I've most of it on the shelf somewhere.

G

[sycamore]

I don`t think you meant what you wrote, vis "has a tendecy to flat spin", as it should have been certificated otherwise.
However, there are a number of reasons / ways you could get into a flat spin; mislandling the controls during a spin-- leaving the power on ; deliberately doing so; and, the a/c`s Cof G is too far aft( outside certification).

Usually flat spins are entered by applying power, and letting the gyro. precession of the prop. bring the nose up to a flatter attitude, increasing the yaw rotation as it does. This will have serious consequences for the a/c if prolonged, depending on the type, as metal props have parted company, damage to wing fuel tanks/ fuel surge, due to centrigugal forces, and although rate of descent may not be high, the instruments may also be in error due to the distorted airflow around the a/c, and may be difficult to abandon- if it doesn`t recover.
Other professional aero experts will undoubtedly offer their advice , as I would reckon you would not be posting if you were one--- I would not be inclined to go off and try anything near flat spinning until I had done all the conventional practice, and done
demo`s with a few recognised aerobatic pilots.
Can you be more specific about the type: Cap, Zlin , Pitts, Yak, Extra? and don`t forget to check the Cof G!!!

[Miserlou]

Hoey50
More specifically, what type are you talking about?

[hoey5o]

Yak 52 chaps,
According to the appropiate reading material it can/will flat spin off poorly executed stall turns .

[Wizofoz]

Yep,

Power plus crossed controls can equal flat spin.

hoey50, are you familiar with the Beggs/Mueller (sp?) recovery? It would be useful to deliberatly flat spin your aircraft both upright and inverted, perfect standard recoveries, then try this one, as if it works in your aircraft it will recover you from EITHER an upright OR inverted flat OR normal spin.

Basically it consists of three steps:-

1) Release stick

2)Close throttle

3)Apply rudder to whichever pedal offers the most resistance.

This has been shown to recover the vast majority of western aerobatic types, and is useful in that, in an unintentional spin, identification of wether it is upright or inverted can be a problem.

Do some reseach and ask someone familiar with the type (and who shares a common langage with you!) but it may be a useful arrow in the quiver.

[747FOCAL]

Wizofoz,

I am a little scared of suggesting a technique to recover from a flat spin or stall without knowing what kind of aircraft we are talking about. Is this a commercial sized aircraft. Having been through so many heavy aft CG stalls in commercial sized aircraft I know they all recover very differently, especially T tail aircraft in wind up stalls.

I am not trying to be a jerk or anything, just scared somebody may try something that gets them killed. :(

[Wizofoz]

747F,

The Yak 52 is a two seat ex-military trainer, bigger than a chipmunk but smaller than a harvard. Not being certified, it may indeed have "interesting" spin characteristics, but it has been used by the soviet block in large numbers for a long time, so I would think there is a lot of info on it out there to be found.

[Genghis the Engineer]

I've never flown or worked on the type, so have no detailed knowledge, but...

I've chatted flying to many Yak pilots and never heard suggestion of a flat spin mode. I wonder if this is a bit of poor translation - virtually any aerobatic aeroplane has potential to spin off a stall-turn, but I can't see anything in that particular manoeuvre that's likely to lead to a particular spin mode - that is more down to power setting, immediate pilot actions following departure from controlled flight, and a small element of luck.

Pure conjecture on my part I hasten to admit.

G

[747FOCAL]

Wizofoz,

Sorry. Did not realize you knew what kind of plane it was.

:)

[sycamore]

Hoey, if you on this side of the galaxy, try .www.skytrace.co.uk, as Gennady Elfimov is a Russian Masterclass at aeros. You may also get more answers on the Private Flying Forum. A lso read on the Safety/CRM forum reg the last Yak fatal accident by the AAIB.
I have done a reasonable amount of flying in -52, teaching formation, tail-chasing/ combat, and aeros, and it may fall out of stall-turns, or leave you pointing uphill, but if all else fails you brace all controls and it will point downhill again. Only if you mis-handle, and put the stick all around the cockpit will it depart. However, as I said earlier, get a professional aero instructor, familiar with the Yak to teach you---first....

NB point noted re hoar frost--- it just lasts longer if the ambient is below zero..
Syc:ok:

[hoey5o]

Thanks for the comments guys.
I already intend to fly with the Russian guys when I can arrange it (skytrace etc) although I believe due to most of the 52s being on the G-register now, there were problems with their licences and so problems staying here to work.
Genghis, it is a fact that the 52 will flat spin readily ( well known)
I really just want to find the best literature possible on the subject so thanks for the pointers.

[Miserlou]

I've also never heard of the -52's tendency to spin flat but all aircraft will have a tendency to flat spin, and usually inverted, from a poorly executed stall turn.

Too much or too little foward stick will give you you the exact combination for a flat spin and the aircraft is perfectly placed to enter it, ie full power, full rudder and close to zero airspeed.

There's no mystery and I'd hate to see the Yak getting a bad reputation for this.

[Genghis the Engineer]

I claim no credit for the following (apart from editing out one or two possibly irrelevant bits), it comes from a friend who is an aerobatic hooligan and a Yak-52 owner...

Incidentally Houey, although you seem to be entirely correct about the Yak-52 flat spin - at-least according to my friend the Yak owner, I've professionally dealt with a number of issues that were "well known" such as the alleged Bulldog unrecoverable spin, which never stood up to rigorous scrutiny.

G




Yak spins well, but there is the risk of getting into a flat spin.
Particularly if you keep the engine at full bore. Flat spin usually results from a 'ballsed up' stall turn. Which is why we've banned that manouvre in the syndicate. There is a mild disinclination to not come out of it, particularly if you've got some power left on.

If your rear seat passenger is heavier than the front seat pilot, there is also an increased possibility of getting into a flat spin from a normal spin or ballsed up aero. This is due to rearward CofG. This is much more of an issue to recover from.

The biggest problem with recovering from a flat-spin is that it requires about 3000ft.

There are a couple of fatalities I know of in Yak52s from flat-spin
issues. First was in ***** where the rear seat passenger was a bloater. The second was at *****where a pilot decided to show how good he was at low level stall turns..... turned out he wasn't.....


The main thing about the Yak52 is the tendency to flick from a G-break or stall. This can rapidly lead to disorientation and either a flat spin or inverted flat spin.

However, you do get quite a bit of warning and if you cut the power wait until you recognise which way up you are, and then apply standard recovery techniques, its not an issue. In worst case scenario, you may need a little aileron in the recovery.

On approach we prefer to use about 1/3 power and use the glide slope on a curved approach, rather than 'dragging' her on. This ensures you remain above the stall and do not get behind the drag curve.

[hoey5o]

Thanks for digging something out Genghis.
Can I just say that I am not attempting to give the Yak a bad name, I think its great. I simply want as much information on something the aircraft can do that I dont know much about.
In the past I got to know the Bulldog very well indeed and I agree entirely that there is no spin problems at all.

[Miserlou]

And there's nothing specific to the Yak in the text supplied in Ghengis' post.

All of that would be true whatever the aircraft.

[crackerjack]

I think that if you can't stall turn your aeroplane safely, you should shouldn't be doing aeros solo. It is after all a very basic figure. Sorry to be dull about this.:confused:

[Miserlou]

It's not about stall turning safely. When you start introducing vertical rolls or slower entry speeds due to the rest of the sequence then you can get too slow at the top. It just happens.

[Lowtimer]

Hoey5o,

I've had flat spin training in the Yak, and have never found it frightening though it can be quite uncomfortable on occasions. I'm not an instructor or a TP, so on such a safety-critical subject I don't really want to write lots into a public archive which others may rely upon, possibly unwisely, any time in the future. I think you're wise to seek a good few spinning sessions with Genna if he's available, or if you want an alternative you could try Ian Austin, based in Cambridge. Don't want to bust the rules on advertising on PPRUNE but if you like I'll PM you with my experiences and can give you a contact number.

Hope you enjoy the Yak, it's a great machine, we love ours!