60 Bank Emergency Decents in IMC

[John Pleisse]

Jeff Van West of IFR and Avweb and Thomas Haines from AOPA have both written recent articles about emergency decents in IMC. They both suggest a 60 degree banking spiral manuever, which strikes me as risky. They suggest this manuever (if practiced), is great to have in one's repetoire, but they don't provide exact yields in decent rates. I get -2500fpm, no power and dirty, wings level. 

In effect, you would be doing a controlled spiral decent. Does anyone practice this? I find it flirting with the one thing we all try to avoid. A spiral.

[tony]

Sounds a little too close to "graveyard spiral."  I think you would need to be very well practiced to pull this off in actual IMC.  It's a lot different doing this for real when you processing all the other information.  I'll be passing on this though.  YMMV.

[bnicolette]

If you need to make an emergency descent, I don't see anything wrong with this technique unless one is not proficient enough to manage it.  However, a 60 degree bank in a descent initially is not a big deal.  I think what they are basically trying to say is that they want you to "unload" the wing and get the thing going down in a hurry without causing any negative g's.  We do this all the time in the jet simulators in an emergency descent, but one certainly wouldn't want to keep the turn going, it is just to get it going down.  You can only go down so fast before you hit Vne anyhow.

[jlunseth]

Yes, no thanks.  I can think of a bunch of things that could go wrong with that.  One, you are at the maneuver limit of the ac.  Two, being that close to the maneuver limit you could go a little too far too fast and tumble the AI (you are in IMC, remember).  Three, having done an emergency descent in IMC, you discover about half way through that you knew how high you were when you started, but had not found out how high the ground is, and therefore where you will meet the ground.  You ask ATC.  You don't want to be asking ATC when it is already too late.  Last, but hardly least, with your gyro tumbled or on the verge of tumbling, a turn of that magnitude creates really strong sensations in the pilot doing it, and unless you have alot of aerobatic training, you probably would not know what they meant.  Not to mention that you are now in a bank that takes your Load Factor to its 3.8 limit very fast.  Anybody remember that from Commercial Ground School?

Unless you are on fire and your only choices are burn or crash, which is it going to be, straight ahead, speedbrakes deployed (if you have them), is the best way.  Dropping gear in a descent like that means exceeding Vge in the dive, so expect the gear not to like your very much. 

[John Pleisse]

Yeah, but Brett..you are a corporate pilot. Spacial disorientation is the biggest danger in IMC for amatuers, especially solo IMC. Sure you don't hold altitude creating load and Van West stipulated speeds of near Va. Is this standard practice with a big jet? If I get -2500fpm, level, dirty, no power. How much more would one get doing the spiral manuever? -4000fpm? Anybody done it? Is it smart for aviation authors who have time and accesss to recommend it to 50 hour a year laymen? Or is this just not that big of a deal?

I am out for a new fuel pump this week ($1200 smackers), otherwise I'd grab a CFI and go try it vmc.

[Bennett]

Years ago I was taught this technique, and I once had to use it in an emergency.  I was at flight level 230, in winter, staying just above some substantial clouds in my Mooney 261, when I lost power, really big time.  I suspected it was a turbo failure, and I had visions of fire blasting against the firewall.  I wanted to get down NOW. I knew I was over Big Bear (CA), and that I was well within gliding distance to Palm Springs airport. I delarered an emergency, and LA center confirmed my position, and said they would clear the area, which they did.  I slowed the aircraft to gear speed, dropped the gear, flaps out all the way, put the speed brakes out, and banked about 55 degrees, keeping the nose down to maintain about 110 Kts or so, with just a bit of of top rudderas recall as I spiralled down at about 3000' per minute. The clouds were quite thick, and at one point I encountered snow, but I broke out at about 3000' AGL, and was able to make the airport in a far less steep spiral. Palm Springs tower cleared the airport for my landing, and it was a non-event.  As soon as I was on the ground I called LA center to thank them for their help, and asked them what paperwork I would have to file.  Her answer was "We did our job, you did your job, it all worked out OK, that's all I need".  Wish the FAA was that way nowadays.  Anyway, my old instructor (Commercial/Instrument) made me practice that maneuver many times before, in the clear and under the hood, and so there was no unfamiliarity with it, but it still was scary, and I wouldn't recommend anyone trying it without practice, and perhaps it would be best with an instructor. 

[bnicolette]

John, you're right.  It is something I would do just out of instinct and that's what we practice every year at training, but there is no danger in doing it, IF you are proficient in doing it. I have to believe thought that your are absolutely right in that the safest way to do it, is bend it right on over straight ahead.

jlunseth - There is no increase in load factor when doing this maneuver unless you are defeating the purpose and staying at a constant altitude.  Also, I have banked over 90 degrees in other single engine airplanes, spun many tired training airplanes and Never had an attitude indicator tumble on me.  If the attitude indicator decides to tumble from a 60 - 90 degree bank, perhaps it's a very tired indicator, which is why I always carry 2. 

John, I would be interested in seeing what kind of descent rate this puppy will give at Vne, and yes that is the procedure in the Jet world although it's called Mmo.  In Mr. West's instructions, are you to keep the turn going?  Or is it just to start the descent that much faster by unloading the wing?  In training we actually knife edge the plane and let it fall through the horizon naturally, this will keep from getting any negative g factor and also so we don't block the airflow from the intake of the engines to preclude a flameout.

John if you have that article somewhere handy, I would like to read it.

Thanks,

B~

 

[John Pleisse]

Well..here's another thing. The manuever requires opposite rudder (imposing some load). Sure no load is imposed if you keep the thing pointed down, but I gotta think if you let up a little or if out of fear of the emergency one pulls or tugs the yoke...you gotta be begging for it. It would have to be instinctive.

[John Pleisse]

Oh Brett sorry....

John if you have that article somewhere handy, I would like to read it.

He goes through it on Avweb in a video and it is the cover story of this month's IFR that just arrived today. Thomas Haines did it a couple of months back in AOPA. He chronicled the manuever with a local and famous Bonanza instructor (also G-5 pilot), Adrian Eichorn.

[Jerry 5TJ]

I recall doing approximately this procedure in single-engine turboprop.  The drill was

• 
  
• power to zero thrust
  
• gear down
  
• speedbrakes out
  
  
• 60 degree bank
  
• accelerate to redline (top of green arc in a turbine)
  

in a P210 with RR turbine, the descent rate reaches 6000 fpm.  I remember the descent felt fully stabilized.  Likewise in the TBM700 a similar procedure gives about that same (impressive) descent. In the M20C the low gear speed of 105 knots limits the descent rate greatly but the maneuver is stable, and in the M20C your cruise altitude is rarely so high that a 2000 fpm descent won't do the job.

 

[DaV8or]

I wonder, if those of us that are uncomfortable with this manuever could maybe use a lesser bank angle? Would say 30 degrees bank or standard rate get you down faster than just straight ahead? Seems like a power off, gear down, flaps out decent in a standard rate turn would get you down faster than just the same straight ahead and still be managable for most of us. Sort of a compromise. 

[jetdriven]

they used to teach people to spin down through the clouds  and then go along their merry way back in the Champ and Cub days.  Hopefully the clouds didnt reach to the ground.  

 

Whats wrong with the current 180 degree rudder only turn they teach now?

[Shadrach]

If I really needed to get down in an emergency situation (eg. fire), gear speed would cease to be a concern... Gear down, 45degrees of bank decent at just under VNE...

[jetdriven]

David from All American said the gear speed is only becasuse of the doors.  Which can be replaced.  The landing gear can be deployed at any speed without concern for structure.

[jetdriven]

Shadrach, don't forget 1" per minute!  You dont want to shock cool your cylinders!

[Shadrach]

Yes I know that the doors are the limiting factor... However, I can tell you that it's not gauranteed that anything will happen to the doors... As a fresh Mooney pilot, there were 2 occasions when I did not get the J-bar quite locked in the retracted position.  As I am sitting fat and happy in cruise at 150kts, I suddenly see the J-bar come shooting up between the seats...  

[Cris]

Some years back I was flying a mission as an aircraft commander for the USCG auxilliary. We were transporting regular Coast Guard personnel thru Kennedy air space in solid IMC conditions in an M20J. The Kennedy controller asked for an "immediate" 360 & maximumum descent to 2000'. The maneuver discussed was implemented from 5000'. I had practiced this for "fun" many times so it was no big deal but the relief in the controllers voice was obvious once at the requested altitude. Never did learn the cause of the request but I was glad to accomodate.    

[bd32322]

any amount of bank angle would work - just not as much as a 60 degree bank - you are basically dumping lift.

a close cousin of this would be the falling leaf maneuver   - bank left and bank right and repeat - maybe these were called dutch rolls by my aerobatics instructor - dont remember now - that will also give you an impressive rate of descent without changing your direction of flight.

but again essentially you are not letting lift hold the plane up - you are losing it in a quick series of left and right banks - thus giving you an impressive rate of descent. This is not a good idea in IMC because it is not as stable as a continuous 60 degree bank. But fun to try on a VFR day with sufficient clearance from mother earth.

[Shadrach]

I do not see how this relates to a falling leaf?  In the falling leaf manuever, critical angle of attack is exceeded...it is power off maneuver in which the wing is held in the stall with pack pressure and the rudder is used to control yaw. Basically a continous insipient spin to the left, then to right, then to the left, then to...etc...until the AOA is allowed to return below critical levals. I'd prefer not to do this maneuver or anything "close" to it in a Mooney and certainly not in IMC...

Banking in the decent simply removes part of the horizontal component of lift. As the nose falls the plane is allowed to descend toward vne the wing is in about as opposite a condition to "the falling leaf" as it can be with regards to critical AOA...

[bd32322]

shadrach - i clearly had my falling leaf maneuver messed up in my mind - maybe its called some sort of roll. From what you describe - definitely not worth doing in IMC. But was just trying to point out that all you need is bank to lose lift and to lose it in a straight line you can bank left and right in VFR without rudder - and you dont need to take it to the extreme and stall a wing - because at that point you should spin - which is prohibited.

i guess its more of an un-coordinated s-turn maneuver.

and no - it does not relate to a 60 degree bank low AOA turn - but was just pointing out another way of descending without changing heading - i guess its a bit off-thread.

[Shadrach]

What you're describing sounds like a very aggresive turning slip in one direction, followed by a very aggressive turning slip in the other. This is a certainly a method of descending quickly, and by reversing direction you are in effect S-turning which would extend the relative distance traveled giving you more time to get down. I've never done it, but if circumstances called for i, I would...It's another tool in the shed. I'm pretty sure that it would wreak havoc on your inner ear in IMC though... ;-)

[bd32322]

definitely not in IMC - when you are bored on a VFR day - and really I did this in a decathlon - on a mooney i think my arms and legs would give up before I did too many turns.

 

[John Pleisse]

erry-N5911Q

Senior Member

Joined: Oct 19, 2009

Posts: 106

Location: San Rafael CA USA

Re: 60 Bank Emergency Decents in IMC

Posted Jun 22, 2011 9:24 PM

I recall doing approximately this procedure in single-engine turboprop.  The drill was

power to zero thrust

gear down

speedbrakes out

60 degree bank

accelerate to redline (top of green arc in a turbine)

in a P210 with RR turbine, the descent rate reaches 6000 fpm.  I remember the descent felt fully stabilized.  Likewise in the TBM700 a similar procedure gives about that same (impressive) descent. In the M20C the low gear speed of 105 knots limits the descent rate greatly but the maneuver is stable, and in the M20C your cruise altitude is rarely so high that a 2000 fpm descent won't do the job.

 

Jerry...this answers it. Completely.

[Shadrach]

If I'm on fire at 9800AGL -2000fpm probably aint gonna do it for me... at that point, VLE is merely a number that I will gladly watch the ASI needle sail past on it's way to VNE...

[jetdriven]

if you are on fire remember the early M20 airframe was tested to 300 knots.