Aerobatics question
 

A (non pilot but with some experience of gliding) friend of mine was given an aerobatic lesson for a present in a C152 Acrobat. He was regaling the exploits tonight and told of a flat spin entered at 3000 ft AGL, recovered at 'slightly less than' 700 ft.

Now, I've never flown acrobatics and don't have any desire to. But to me that seems incredibly reckless - not to say bordering on the illegal as 'slightly less than' 700 ft is only 'slightly more than' 500 ft. I'm hoping they were flying on QFE rather than QNH !

I was wondering whether this was normal practice ?

An intentional spin recovery at 700 feet AGL is reckless, and certainly not "normal" - do not participate in flights like that! A 152 Aerobat does not really "flat spin" it just spins. If something has been done to alter its spin characteristics, the aircraft is out of limits, so don't fly in it!

Spins are great practice, but like anything in a plane, they should be flown with caution, and respect!

The Aerobat will indeed spin flat.

I certainly agree about that low recovery height - especially with a passenger.

What in an Aerobat would be the difference between a flat spin, and a "regular" spin?

Referencing Stall/Spin Awareness by Rich Stowell for NASA spin mode classification: steep 20 -30 deg angle of attack, moderately steep 30-45 deg, moderately flat 45-65 and flat 65-90 deg. So, 45 deg and more is flat.

The Basic Aerobatic Manual by William Kershner and a Flight Magazine article of 28/10/78 provide info on pitch attitude in a fully developed spin with normal controls. 45 deg nose down (which equates to 45 deg angle of attack) can be achieved although usually about 70 deg nose down and sometimes spiral characteristics - CG is a factor.

Try some aileron. 60-Turn Spin in a Cessna Aerobat! - YouTube

I have never experienced abnormal spin behavior in a SEP Cessna but an instructor I know experienced a flat spin in a C 150 Aerobat. The spin attitude was essentially level with a high rate of rotation and spin recovery control inputs had no effect. He recovered by applying full power and full into spin control inputs. The aircraft shook like a wet dog, gave a massive lurch and transitioned into the normal nose low spin attitude. After that power was reduced to idle and a normal spin recovery carried out.

It was a bumpy day and the instructor thinks the aircraft experienced a large up draft just as the spin was entering it's second rotation causing a pitch up just as true auto rotation started and leading into a flat spin. Since he was an aerobatic instructor he was able to recognize what had happen and recover. I think an ordinary non aerobatic instructor and his student would almost certainly spun into the ground with fatal results.......


The bottom line IMHO is simple: Just because the aircraft has done 10,000 perfectly normal spins doesn't mean that the 10,001 spin will not require an aerobatically trained and experienced pilot to recover

Any pilot that has not had formal aerobatic training, including full normal and abnormal (ie flat, inverted) spin training should not carry any spin past the spin entry phase. That is 1/2 to a maximum of 1 turn. If the aircraft does anything unusual in the spin entry an immediate recovery should be carried out.

If he was a non pilot I doubt he would be able to recognise a flat spin from a normal one so not sure if they actually did that, a normal spin or a spiral dive, whichever it was the recovery height was ridiculously low even solo, with someone else on board the guy should be fired!

My one and only trip in one of those things and it was nigh on impossible to keep it in a spin after about 1 1/2 turns but that doesn't mean things can't go wrong - if you are doing no more than 1 1/2 turns 3000ft is not an unrealistic entry height.

I would guess the recovery at 700ft was more likely because that's how long it took them to recover, rather than a deliberate attempt to put in 4 or 5 turns from 3000ft

however I would doubt that it was 700ft.... you'd be properly cacking your pants, I don't know what the rate of decent is in a 150, but imagine a good 5000-6000 ft per minute minimum....

Ah okay, if that's how we're defining it. My experience spinning Cessnas has shown that they will sometimes bob up and down a bit, so there might be elements of both flat and normal by that definition.

That said, however, and with deference to BPF's remarks, a 152 Aerobat will spin about the same per C of G position - it does not have skeletons in its closet. Thus I prefer just say we're going to spin, and leave the drama terms aside. For my experience, the term "flat spin" suggests a real problem getting the nose down to recover, and thus an alarmingly delayed recovery.

I have only experienced this once, while spin testing a modified Cessna Grand Caravan, loaded to gross weight, and the aft C of G limit. It did come out within the design requirements, but that one turn in, and second turn out were very un-nerving, as to the delay in response to full nose down elevator applied and held. This was dramaically different from the characteristics I had observed in that aircraft the day before loaded gross weight full forward C of G. Thus, I was reminded that the aft C of G limit is determined by spin recovery characteristics, and not to exceed load limits.

That all said, in my opinion, Aerobats spin. Spinning beyond a turn or two is a wasteful and needlessly dangerous activity, and safely spinning them requires a recovery to be complete at an altitude greater than 1000 feet AGL

Cessna 150s are reluctant to spin, usually preferring to spiral dive despite one's best efforts to spin it. During my PPL we used to do flick entries to spins - that usually worked!

However, like many aeroplanes that don't usually readily spin, sometimes the C150 will spin quite viciously in a very real and hard-to-recover spin. But I suspect, as has been said, that a non-pilot would not know a flat spin from a normal one, or even from a spiral dive.

I practiced flat spin entries and recoveries with Genna (Mr Yak) in the Yak 52. They felt quite different to 'ordinary' spins and required in-spin control inputs in recovery. The rate of descent was prodigious!

A trickle of power does the trick during entry.

As for the Yak, great fun but :eek:

As an experienced aeros and spin instructor I would be looking to recover by 3,000', not enter there!

Foxmoth,

maybe for sensible practicing initially, hell in the uas we used to clamber up to 10,000ft for 3 turn spins... but its no good for competitions...

So a witness who is a 'non pilot with some gliding experience' attests to a flat spin and we all jump on the professionalism of the C150 pilot? Is this not a bit like the the tale of the couple recently who had their honeymoon ruined by the terrifying actions of their pilot... it was a Go Around.

Jeez guys, if you're going to bring into question the professionalism of a C150 pilot, don't do on the back of testament from a guy who didn't know what he saw.

All of the Cessna fixed gear SEP POH's give the same information:

Quote

It is recommended that all spin entries be accomplished at a high enough altitude that recovery is completed at 4000 feet AGL. 1000 feet of altitude loss should be allowed for a one turn spin.

Unquote

Seems pretty clear to me.........

I saw nothing to say this was a competition - both comp and display you are either solo or with someone even more experienced than you are, NOT flying someone inexperienced - even solo I would not be recovering as low as 700' unless I was working up for a display or comp.

Fox,

I take you point re competitions but as far as the OP we have no way of knowing how accurate this info is. The entry height could have been 5000ft and they are both lucky to be alive or 700ft is a figment of an imaginative mind, maybe he dropped the 2 in front for artistic license.

personally I think its a figment of imagination. like the time someone at a party was telling anyone who would listen how went up in a extra 300 with ultimate high and did -6g.

Unlikely yes, but put someone who is up for it in the Extra and certainly possible - I have certainly had a few in the Slingsby that have done -2.5 no problem (also had a few that I have suggested a gentle fly around after two or three aeros of less than +4!).
There is the Utter Nutter Flight | Ultimate High trip that will certainly push many people to their limit and give them some bragging rights at a party!

If this was a figment of the imagination or not, the question was asked "is this normal practice" and I was answering that.

No, it isn't. :eek:


MJ:ok:

-6g is easily achievable in an Extra, although not much fun. A hard push out from a spin recovery would do it if you were going fast enough.

Recovery from a spin at 700 ft would get you disqualified in most competitions, where the floor is usually 1000 ft agl and the judges are pretty good at spotting violations.

I would not fly again with any pilot who did this to me, especially in a semi aerobatic aircraft like an aerobat.