Spinning help

[memnoch]

Hey guys

I was out today doing some aeros and for some reason the plane would not spin :ugh:. Its a C152. We induced the spin by slowing to stall and at stall, lots of rudders and aileron, with sharp pull back. The nose lifted up, we rolled/yawed to the left nose pitched down and begun to dive whist turn around the vertical axis. But speed increasing therefore not spinning. When we tried it to the right and where able to enter. have done this before to both right and left and its worked fine but for some reason today they aircraft wasn't wanting to spin. :{ .

Any thoughts?

[hongkongfooey]

As you probably know memnoch, what you have described is a spiral dive, basically similar to a spin but not stalled, so a very quick increase in airspeed, things can go pear shaped very quickly.:eek:
I am by no means an expert on spinning, have only spun a few different aircraft ( not C152 ) and not for some time but I'm pretty sure to enter a spin I never used aileron ( ie aileron neutral ), just full rudder and full backstick holding the full backstick until in the spin. On occasion despite doing everything " textbook " the a/c would enter a spiral dive ( to be honest crapped myself a little the first time ).
Hope this helps
Cheers

[memnoch]

yeah we entered a spiral dive, I use a combination of aileron and rudder to induce the spin from the stall.

Yeah crap myself too was like this doesn't look right :ooh:

[djpil]

Entries per the POH work fine, from my copy:
"The normal entry is made from a power-off stall. As the stall is approached, the elevator control should be smoothly pulled to the full aft position. just prior to reaching the stall "break", rudder control in the desired direction of the spin rotation should be applied so that full rudder deflection is reached almost simultaneously with reaching full aft elevator. A slightly greater rate of deceleration than for normal stall entries or the use of partial power at the entry will assure more consistent and positive entries to the spin. Both elevator and rudder controls should be held full with the spin until the spin recovery is initiated. An inadvertent relaxatioon of either of those controls could result in the development of a nose-down spiral.
NOTE
Careful attention should be taken to assure that the aileron control is neutral during all phases of the spin since any aileron deflection may alter the spin characteristics by increasing the rotation rate and changing the pitch attitude."

If you do enter with a bit of power, close the throttle fully once it is rotating.

I suggest that you also read the subsequent page on recoveries.

More info on spinning Cessnas online here (http://www.flightglobal.com/pdfarchive/view/1978/1978%20-%202617.html?search=cessna%20spin).

[Dog One]

It would appear that the aircraft may not be stalling fully. I remember that some of the C-172's with the drooping leading edge (post 1974) were hard to induce into a spin. If my memory is correct and its the same aircraft you fly all the time, try wings level and power on up to the stall.

If it was a different aircraft to the one you normally fly, it may be rigged slightly different, ie not enough up elevator, to the aircraft you normally fly.

[grade-3]

How was the aircraft loaded and where was the CofG located?

A forward CofG would reduce effectiveness of nose up elevator (due to the increased nose down pitching moment caused by the lift-weight couple), so the tail down force generated mightn't be sufficient to hold the aircraft in a stalled condition.

grade 3

edit: Also, stick with the entry technique specified in the POH/AFM - can get quite exciting otherwise! :ooh:

[djpil]

While I'm here, the NZ CAA has an excellent publication on Spin Avoidance and Recovery (http://www.caa.govt.nz/safety_info/GAPs/Spin_Avoidance.pdf).

[By George]

The warning on keeping the ailerons neutral is very true, if you give it a quick jab of aileron in the opposite direction of entry it should increase the rate of rotation. Oddly enough this was standard technique to get some Airtourers to spin when they wanted to enter a spiral dive. As a previous post mentioned the C of G is also very important. I would be very careful of experimenting outside the advice of the manual though. Some of the most innocent of the GA fleet will bite. The AA5 with its spar fuel tank was lethal in a spin as the fuel moved outboard and flattened the spin. Early Chipmunks without the strakes and an aft C of G were also very exciting. The Tiger Moth is still the best spin trainer in my opinion, if you can get hold of one, classic spin characteristics, nose down, fast rate of rotation and instant recovery with standard application.

[grade-3]

It's almost certainly been posted somewhere here before, but Mal Beard's article (http://www.ozaeros.net//spin/beard.htm) on spin recovery is also enlightening.

It includes a good summary of the effects aileron and power have on spins and spin recoveries in various aircraft.

grade 3

[Kiwi172]

Beware of what many of us consider docile training aircraft, they do have a sting in there tail. I have done a lot of aerobatics and spinning in Tiger Moths - having also attended the NZ Tiger Moth Club spin Awareness Training a number of years ago. Recently i was judging an aerobatic competition in a C152. After a number of rotations i told the competitor to recover, nothing happened, i said recover now to which he replied i am and its not doing anything. :eek: By this time we were getting much lower than what i was comfortable with and said I have control. He was right, I put in the standard recovery technique and the C152 just continued on spinning. I cant describe the overwhelming hopeless feeling in the pit of your stomach you experience when after putting in the std recovery nothing happens and the earth is getting very close very fast, not something I ever want to experience ever again.... As we descended through 1000ft I thought thats it we are history, eventually I managed to get it to recover, we were only one more revolution and 1-2 seconds from being a smoking hole in the ground. When it did recover the nose attitude was much flatter to what I am used too, which may have been a blessing as we had to climb back up to 500ft to join for landing. I have spoken to many learned collegues since in an attempt to discover what went wrong. The opinons have been many and varied. One advised let go of everything and it will recover by itself. I have it on very good authority from a very experienced C152 A cat that if it goes flat and you let go of everything, it will not recover itself. Another advised a burst of power to blow some slipstream over the blanketed controls, another advised using the flaps to alter its attitude. It was a very sobering event not only for myself and the competitor but also for the many that saw us dissappear behind a row of trees waiting for the inevitable

[tinpis]

Pull up from the cruise to vertical, leave the power.
When it slows right down
Apply full forward stick and hard right rudder

Let me know how that felt :E

[ForkTailedDrKiller]

Pull up from the cruise to vertical, leave the power.
When it slows right down
Apply full forward stick and hard right rudder
Let me know how that felt :E


Oh dear!

Dr :8

[djpil]

Part of my post in the spin thread at the instructors' forum (http://www.pprune.org/flying-instructors-examiners/286242-spin-recovery.html):
Extract from an article by Gene Beggs in Sport Aerobatics of October 1985:
"In my telephone conversation with Bill Kershner, he told me of a spin mode in his Cessna Aerobat from which he was unable to recover using my power-off, hands-off, opposite-rudder method of emergency spin recovery....…
If I placed the aircraft in a spin to the left with the power on as might happen with a student who did not correct for the “P” factor properly, and let it spin with the power on for two turns or more, and then cut the power off, released the yoke completely, and then applied full right rudder and held it, the aircraft would continue to spin and showed no sign of recovery evern after as many as 10 turns! I would then place the heel of my hand on the padded center portion of the yoke and briskly push it forward, and the aircraft would always recover promptly in one additional turn ....
I found that the Cessna 150 would spin very docile, as long as the ailerons were held neutral and the power completely off in either direction .. Trouble developed only in the spin to the left, either when the power was left on or when “in-spin” aileron was applied and the aircraft permitted to turn two turns or more ..."


tinpis - I'd use aileron there too.

[Mark1234]

If it entered right, and not left, then it's probably not rigged straight? (or perhaps a fuel imbalance)
COG - fuel on board and fatness of pax most likely the cause of differences..
Aileron - would depend in which sense you're using it - trying to pick up the inner wing would help, rolling into the spin would promote a spiral dive.

BUT

You should probably know all that if you're messing around with spinning; sounds like a bit of a recipie for disaster.

Also be sure to read the manual - I'm lead to believe a 152 recovery is not entirely standard (Kiwi 172, you may now be aware of this :E) They also have a bit of a reputation for having some interesting and varied spin modes. Haven't spun one personally, but I'd be well read before I did..

[ab33t]

150/2 will recover on their own if left neutral and power off after two rotations. The things is , if all things are equal , pax and pic fuel and CFG

[CHAIRMAN]

"The Tiger Moth is still the best spin trainer in my opinion, if you can get hold of one, classic spin characteristics, nose down, fast rate of rotation and instant recovery with standard application".

Awesome spins, but not too sure about the 'instant recovery', unless you cheat with a bit of outside aileron to slow up the rate of spin.

[Fred Gassit]

My experience with C152 spin entry was similar to yours- when applying pro spin controls approaching stall speed, sometimes I spun, often I spiralled, it felt like the aircraft really doesn't have the control authority at those lower speeds to reliably stall the wing-(without a bit of extra prop wash or longer control moment as others suggested).

I found that an accelerated entry (basically snap roll) was the most reliable way to get a stable spin developed.
From these modes the a/c always needed a positive recovery.

The other thing too keep in mind is if its difficult to spin, for many of the same reasons, it may be difficult to recover.

[Sunfish]

My comment is "Be careful what you wish for, because you just might get it".

My limited understanding and experience is that;

1. Flat spins may not be reliably recoverable.

2. An Aft CG position may flatten your spin, which is why you need to pay very careful attention to CG position (eg Alpha 160 - no more than 110 ltrs of fuel)

I must get out more and back into learning aeros.

[aseanaero]

Perhaps you are subconciously relaxing back pressure before the spin properly develops ?

Also check the CoG and that full rudder and elevator deflection is available.

Ive spun aerobats many times and never had one that wouldn't go into a spin if back elevator and full rudder is held but I also was aggresive in getting the nose up high before spin entry, at least 30 deg.

Also take notice of some of the previous comments , if you are doing everything correctly it could be a CoG problem especially if both pilots are heavy and if you get it to spin it may not come out, I know of one acquaintance that spun one and didn't survive and the accident report showed an out of limits rear CoG.

[toolowtoofast]

Thanks for sharing that Kiwi - I have heard that your incident looked very scary as you descended below the trees.

The OP stated that they waited for the stall, then aileron/elevator/rudder. It is possible that at the stall, when yawing with rudder, the use of aileron could balance the advancing wing's lift with the retreating wing's lift - the change of camber on the retrating (more correctly- slower) wing with aileron input *could* balance the advancing (faster) wing's lift envelope. Depends on what aileron was wound on, but I am suspicious that the OP is not sure - I have never heard of aileron and power being used in anything other than accelerated spinning (yes I have done acellerated spinning in the appropriate aircraft - I wouldn't do it in a 152). Just a thought.

And I have always initiated a 152 spin a little faster than the stall - it has ALWAYS gone left easily, but as has been said, if you are not holding FULL elevator and FULL rudder, it will more than likely recover after the incipient.

[MakeItHappenCaptain]

justapplhere:

Was it legal for you to spin those C172's?

Not sure for all models, but for example in the C172N, spinning is permitted if the aircraft is flown in the utility category (2000lbs Max Wt down from 2300lbs and nothing in the back seat or cargo area).:ok: