Flat spins

[FlyingForFun]

A question or two for some of the aerobatic experts:

When I first did some aerobatics a few years ago, I was taught to use power during a spin to flatten the spin (in an appropriate type, of course). As power was added, the spin flattened out noticeably. We then removed power before recovering.

Since then, I've done a bit more spinning, here and there, in various different types including C150/C152. I love spinning, and haven't yet had any problems, but I do have (I hope) a healthy dose of caution every time I'm planning on spinning.

Yesterday, I found myself spinning a C152 Aerobat - one which I hadn't spun before. Other pilots who had spun this aircraft told me that it sometimes doesn't enter the spin very well, and a bit of power may help. I had a very good read of the relevant pages of the POH beforehand, and found something very similar in the POH. (Don't have it to hand, but it basically said that it may be necessary to use a small amount of power prior to the elevators reaching the full-aft position.)

I first tried a spin without any power, and found myself in something that looked more like a spiral dive than a spin. Recovered from that, climbed back up, and used a touch of power on the next try - and this time it spun just like I expected it to.

Ok, so the question: What exactly defines a "flat spin". How much power do you have to add before a spin becomes "flat"? Or is it just one of those gradual things, with no clear point at which a regular spin becomes flat? Would the spin which I did in the Aerobat count as flat? It didn't look very flat to me, despite having some power on.

And also, what would happen if I "forgot" to remove the power before trying to recover? This is something which I would ideally like to try (with someone who has more aerobatic experience than me!) rather than just read about. But during yesterday's spinning detail, the student I was flying with tried, several times, to recover without closing the throttle (despite me briefing him thoroughly beforehand on the correct technique - but we know how disorienting your first ever spinning session can be, so I don't blame him at all). I made sure I was quick to instruct him to close the throttle (and pushed his hand out of the way to close it myself once when he was a little slow)... but that was only because of my ignorance of what would happen if the throttle wasn't closed. Would it have been safe to allow him to recover with the throttle still slightly open? My thoughts were around possible engine or airframe overspeeding, but I would imagine it would also have an effect on the recovery itself?

Thanks!

FFF
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[stiknruda]

F3 - have read yr post but currently don't have the capacity to write enough words to help you out!

Will respond Mon or Tues.

HOWEVER - if you have no experience in the spin regime that you inadvertently find yourself in, CLOSE THROTTLE, APPLY rudder to oppose yaw and bring stick to neutral (works errect or inverted) and fly aircraft out of ensuing dive!

Another way of flattening the spin is to use aileron..............

Most of us aeros pilots quite frequently inadvertently spin with power on - if intentionally activated the aircraft "flicks/snaps" in to the spin.

For recovery - Muller used to advocate outspin aileron, back stick and a tadge of power!

Cassidy - wrote a great article on unspinning the Bulldog with power about 15? months ago.

More soon unless DJ Pilki or somebody else steps ino the breach first


regards,


Stik

[LowNSlow]

FFF The first time I spun a 150 (non Aerobat) was during my PPL as I was terrified of the prospect of spins so asked the examiner to demonstrate. After the ashmatic little Cessna had staggered to 6,000' (We need lots of height, I don't trust this thing. Gee thanks.) the spin was demo'd. Wheee thinks I, lets have a go at that.
Stick back, bootful of left rudder and open throttle wide. Damn that thing went around fast I've never seen an instructor move as fast as that chappie did when he pulled the throttle closed.
So, I don't know about flattening the spin but an open throttle makes them turn really fast but the wings do stay on.

[BEagle]

Cassidy's article on Bulldog spinning was most certainly not viewed as a 'great article' by everyone!

Why on Earth anyone should 'enjoy' spinning is beyond me. I used to teach spinning and suffered a few student handling errors as a result. Never could spinning be thought of as 'enjoyable'..... It was an essential part of the training we delivered and was straightforward enough to teach, but hardly 'enjoyable' in the way low level navigation or 1 v 1 combat were.

Also, there is NO SUCH THING as 'Standard Spin Recovery' - the ONLY way to enter or recover from a spin for training purposes is AS PER THE POH. Nothing else is acceptable!!!

One of the contributors on this thread has already mentioned a recovery technique which, if you tried it in a Bulldog, would probably kill you.

Don't ever take liberties with spinning - and don't adopt non-standard weird techniques thought up by those people who enjoy +10g to -10g.... Such techniques might well work in specialist applications, but are unique to type.

[djpil]

More soon unless DJ Pilki or somebody else steps ino the breach first

Thanks, Stik, I was going to stay out of this one but ...

Apart from the comments on the Bulldog (because I know little about the type - I did get to read the first of Alan's articles though) I agree with BEagle about the need to avoid too much generalisation when discussing spin and spin recovery characteristics. A short answer to FFF's question is likely to be an oversimplification so I'll try to stop with some advice on reading material.

For the types that I operate the Rich Stowell stuff works well. I thoroughly recommend Rich's videos and the new book - Stall/Spin Awareness

Kershner's book, The Basic Aerobatic Manual, has an excellent chapter on spinning the Aerobat including advice on that "bit of power" that FFF mentioned - some Aerobats, especially 152's need to be coaxed into a spin.

An extract from a Flight article from 1978 on Cessna spin characteristics
can be viewed here.

FFF, my advice is that it would be well worth your while to spend some time on the ground with a good instructor on this subject. FFF - I'm happy to continue the discussion later.

[Genghis the Engineer]

Also, there is NO SUCH THING as 'Standard Spin Recovery' - the ONLY way to enter or recover from a spin for training purposes is AS PER THE POH. Nothing else is acceptable!!!

Amen.

G

[hoey5o]

Flying for fun.

With your lecture hopefully over from Beagle may I say I totally understand where your coming from.

Both of us treat the spin with respect which is why you have posted this topic to find out more from the guys who have pushed the boundarys.

I too want to become much more aware of the envelope so your better equiped to deal with a problem (if aeros is your thing).

The RAF in general know surprisingly little about flat spins and do not address it in training. The statement that you should only practise spinning via the POH is absolutley sensible however when are you ever going to inadvertenly enter a spin in POH approved manner !!!

The Airforce always taught the 'incipient spin recovery' (centralise controls) which worked for any attitude as long as you hadnt fully entered a spin. I always wondered what if the aircraft did go flat ? I was never taught what to do if this happened ! Maybe because it wouldnt happen as long as I entered in an approved fashion !!!!!!!!!!!!!!!

There are lots of books/videos out there. Daroll Stintons books contain some really in depth Test pilot stuff on spining but I too have found it a struggle to get good gen on flat spins. As many aerobatic books and videos are a good start, it may also be worth trying to get yourself a one off flight in something that is fully appproved to do it such as the Yak 52 with a russian QFI if they are still here.
If you do get some really good flat spin material could you please pass it on.

[Shaggy Sheep Driver]

I did flat spin recovery training with Genna in our Yak 52 a while ago. The effect of power on and power off in an aeroplane with a heavy and powerful engine is quite marked - far more so than in, say, the Chippy.

Agree with BEagle that the POH is king. And while far from being an expert in spinning, I have a suspicion that the dynamics of a spin can be more complex than most of us realise, with a potential for the unexpected to happen. So perhaps they should be treated with even more respect than other aspects of flight.

SSD

[767bill]

FFF

For your info, there's a good thread on spinning in the Instructors' Forum, I think it's titled "Do you agree/ refuse to teach spins to students".

[Human Factor]

Just out of interest, the POH for the 152 does not approve power on spins. During entry is ok (mainly 'cos it won't go in otherwise - particularly to the right ), during the spin is not!!

[sycamore]

FFF, you may wish to consider a few technicalities, before `forgetting` the throttle.......otherwise.`a fool and his engine/prop may soon be parted`.....
Unless you are flying a fully aerobatic a/c, with a full inverted fuel and oil system, you will find that you may end up with an airlock in a gravity fuel system, due to the high lateral fuel surge, and also no oil pressure for similar reasons. Not only that, the gyroscopic forces on the engine/prop could lead to a sudden`TWANG`, and the CofG somewhere,well behind you.....If it doesn`t happen to you, it may happen to someone else........If ,as has been stated, by several others, it states in the POH/ACM, that you must not, then why go against that.

[Flash0710]

SSD,

Spinning with Genna.....

Nuff said.......



Legend.....

F

[FlyingForFun]

Thanks for the posts so far. Lots of useful information, but nothing which specifically answers my question. Particularly looking forward to Stik's more comprehensive reply when he gets a chance. Mind you, I didn't expect a straight answer!

Plenty of comments about following the POH, which I agree with 110%. Just to clarify for those people who didn't get this from my first post (I think most people did get it, but a small minority didn't). I am in no way suggesting that I will or have deliberately done anything other than what is written in the POH. What I am after is some information on what might happen if I inadvertently do not follow the POH. (The most likely reason for this would be a student not following the briefing exactly, but I suppose there are other reasons, too - we are all human.)

I do remember reading Cassidy's article on spinning, and also reading lots of debate about it on here. My memory suggests that it was specific to the Bulldog, though? If not, I will have to try to dig it up and re-read it, because I can't remember exactly what it said.

FFF
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[eharding]

SSD & Flash0710

Spinning trips with Gena - the flat spin in particular - as you
say, simply the best; development of the flat spin out of a
deliberately botched stall turn, and demonstration of the amount
of height lost is one of those lessons that stays with you. Flew
with him on Sunday, but didn't get time for some spinning
before the weather closed in. Top bloke.

Ed.

[slim_slag]

Didn't Kershner say he couldn't get an Aerobat to flat spin?

As for what is a 'flat spin', some here don't have time for his online book, but Denker has an interesting table which uses NASA studies to classify spin modes. References to the NASA studies are given.

[hoey5o]

eharding could you check your pm's

Thanks

[FlyingForFun]

Slim_slag - great link, thanks!

That pretty much answers my first question about exactly what counts as a "flat" spin. Interestingly, even NASA seem to like using vague terms like "extreme" or "less rapid" rather than giving numbers - although they have given numbers for the Angle of Attack, and I would imagine the other characteristics would vary from one type to another, so being specific isn't possible.



FFF
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[Flash0710]

Ed,

You lucky thing!

I was supposed to fly with him on sat but AV needed a new bit.

Soon tho very soon

[djpil]

FFF, you may wish to consider a few technicalities, before `forgetting` the throttle.......otherwise.`a fool and his engine/prop may soon be parted`.....

My recollection is that the design standard for this type required consideration of all aerobatics except those specifically prohibited in the AFM. i.e. the manual would describe recommended procedures and list recommended entry speed for maneuvers - it does not have a list of approved maneuvers - the absence of a maneuver from that list does not imply that the maneuver is not permitted. (For the sake of this discussion can we ignore the situation of new maneuvers being invented, given a name and then claim that they are not prohibited by the AFM). e.g. stall turns (or hammerheads) are not listed in the AFM - from a separate discussion elsewhere a few years back - this interpretation was confirmed with the FAA - stall turns are permitted.

Flick rolls are permitted, easily leads to a spin with full power. When I teach spinning to budding young instructor students, one exercise is recovery from unintentional spins which puts them in a spin with full power.

For more reading on the subject of effect of power and aileron on Cessna spin characteristics see Gene Beggs' article in October 1985 edition of Sport Aerobatics magazine - I haven't seen his book, similar info may also be there. Gene refers to some verbal info from Bill Kershner about power-on spins in the Cessna:
"... after completing two or more revolutions with the power left on, then cutting the power, releasing the yoke, and applying full opposite rudder, the aircraft would show no signs of recovery even after six additional turns with the right rudder held full in." A brisk push on the yoke was needed.

Power and inspin aileron certainly flattens the spin - let's say moderately flat per the NASA classification, closer to 45 deg than 65 deg.

[5footface]

This link has some good stuff about spinning with specific reference to flat spins in a Cessna 152

Sorry. Link included this time!

http://www.ozaeros.flyer.co.uk/spin/beard.htm