Sunday, March 11, 2012

This is a fairly intense video. First of all - everyone lives, so that's nice.

This is a skydiving flight, normal right up until the pilot accidentally stalls the aircraft while slowing to let the jumpers out. The aircraft then spins, and while hilarity most definitely does not ensue, at least the cheesy soundtrack helps keep the mood light.

Looks like the pilot wasn't familiar with spin recovery. For those of you who aren't, if you ever happen to be sitting up in the cockpit and your view looks like the view of the guys in the airplane, maybe do this:

1. Neutralize the controls, ie move the control column to the neutral position, wings level.

2. Apply full rudder in the opposite direction of the spin. If you are spinning to the left, stomp on the right rudder and hold your foot to the floor until rotation stops.

3. You may need to check forward on the controls a wee bit to break the stall.

4. Once rotation stops, level the wings and ease out of the resulting dive, reducing power if necessary once above stall speed. Remember to ease out of the dive rather than reefing back on the controls and risking a secondary stall or airframe overstress.

You may notice that the magic ingredient is basically opposite rudder - your ailerons aren't gonna work so hot because in order to be spinning in the first place, at least one of the wings is stalled - thus the aileron on that wing isn't going to be very effective.

One thing: Some planes don't recover from spins, so you have to focus on not allowing them to ever spin in the first place. Other planes have non-standard stall / spin recovery techniques, so please be sure of the requirements of your particular airbeast when it comes to stall / spin recovery technique. It's not that hard, but it can save your life.

While I'm rambling on about stall / spin recovery, one of the fun things we do during our recurrent simulator training sessions is that we stall the airplane at night when we are down to minimums on a circling approach. It's an easy scenario and in my world that's one of the few times when the risk of an unintentional stall / spin is higher than zero.

What that means is we set the plane up to circle around an airport when we are only a few hundred feet above the ground, and we put our landing gear down and our flaps mostly down, just like they would be when we are landing. Then we fly parallel to the runway (downwind) and set the throttles to 50% or so, then wait. After a few seconds of deceleration, the plane stalls and it's up to us to get her flying again before we contact the planet a few hundred feet below us. The simulated planet that is - we would never try out a scenario like this in a real airplane. Anyway, stall recovery is a lot more visceral when you see buildings right below you than when we are at 5,000' (the normal minimum altitude for practicing stalls / spins) and it certainly motivates me to act quickly. The sim hasn't killed me yet, but it can certainly raise the hair on the back of my neck when the operator feels like loading me up to watch me sweat.

In our Citations we recover from most stall scenarios by just adding power, but with the gear and flaps down the plane is generating a lot of drag, and it takes a few seconds for the engines to kick up enough power to overcome it, so we can still lose a few hundred feet on a complicated stall recovery. I've had the radar altimeter in the sim call out "Ten" (feet above ground) on a recovery before, which certainly adds an element of intensity to the procedure.

If you have access to a flight sim, try stalling when low to the ground and then recovering. After all, isn't that when prompt and proper stall recovery is most important. Obviously nobody sane would ever do that in real life - simulated earth is a lot more forgiving than the real thing. I feel like a dope for even writing that, but I would hate for someone to read this post and then decide to do low altitude stalls on the basis of it and then have their next of kin sue me.

Taking our new plane out for a long run on Monday and Tuesday, so that will be cool.


Paul Tomblin said...

I've been fortunate that all the IFR flying I've done has been to airports with ILS or proper on-field VOR approaches (none of these VOR-A type things for me) so I've never had to do a circling approach in the real world. The thought of doing one in a jet just gives me the heebee-jeebees. I'm amazed that your SOP allows them.

Frank Ch. Eigler said...

I've done a few, though not in a jet. For me, the worst part of it is not the low level manoeuvers, which you simulate with low VFR circuits and have fun with them. The worst is the responsibility to stay within a mile or two of the runway edges, beyond which obstacle clearance is no longer assured.

Jeremy said...

Sulako, I think you will find that video is a publicity stunt of sorts, and that the spin was planned. As noted, the pilots seem to make no effort to stop the spin until quite a bit later on- I suspect they have done this before and it is a planned aerobatic move of sorts. Now, whether it was appropriate to be doing that while carrying skydivers... not sure.

Riaz said...

Nice post Sulako. I myself fly Skydivers out of Grand Bend Ontario. This can happen so easily that when the jumpers are outside producing that extra drag, you feel it and to keep on jump run it's a tad bit of a struggle.

Good for those jumpers who jumped quickly cause I won't want that weight in the back there!

Just me .2 cents

John said...

The guy in the gray jumpsuit had a loose reserve ripcord as well (dangling silver handle, pointed out by the other jumper in the back), and had he not noticed it, could have led to a premature deployment at exit- and possible entanglement with the aircraft. A crappy situation would've gotten a lot worse. Everyone was lucky.

capnaux said...

Well, planned or not, incredible vid, Sulako. I may be stealing this for my own blog, lol! (With credit to you, of course!!)

While it's theoretically "impossible" to stall our magic A320, we can turn off the "magic" and do it--and we do, in the sim, as you do.

As I recall from basic flight trainin' days, usually with a Cessna (152, 172), you can just let go of the controls and the bird will eventually right itself.

Disclaimer: don't try this at home, lol!

Jim said...

The last Transport Canada Safety Letter quoted their 1999 study (search for TP13748E). Fundamentally, they were looking at whether doing spin recovery training makes much of an overall difference in safety, and found that it makes a marginal difference - because most spins happen low and slow and there just is not enough altitude to recover (my C172 needs about 700 feet, so if you stall/spin at 500' AGL on a turn to final....). That said, I usually ask an instructor to come along for a spin annually, usually after completing the Webster competition. They're fun.

Since Stalls are caused by excessive angle of attack, I am curious as to why you primarily do a recovery through addition of thrust (which works, of course, though it does have lag), rather than dropping the nose a few degrees and then (or concurrently) adding thrust.

Nick said...

I thought the first step in spin recovery is always power to idle. In a light a/c like this the only way to really get into a spin is with power so that should be the first thing to get rid of. I remember with the acronym PARE. Power to idle, Ailerons neutral, rudder opposite, and elevator forward. This last three should be done as near simulatneous as possible