Emergency Descents

luvflyin

luvflyin

Touchdown! Greaser!
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Luvflyin
Smoke in the cockpit. Fire. Passenger just swallowed something and they can't breathe. Passenger is an uncaged pooch and is foamin at the mouth. Passenger says I double dog dare you to get the plane on the ground in one minute. Emergency descents as a checkride maneuver are kinda new and pop up on BFR's. I got one a couple years ago and confused what the CFI wanted with an engine out. It surprised me that he didn't just pull the throttle and say "now what" so I pulled it and started in on the engine out boogie until he said not that and explained it to me. The FAA recommended procedure goes something like pull throttle, 30-45 degree bank, pitch and trim to Vfe, drop the flaps and hold it at the top of the white arc and spiral down. Sounds like a reasonable enough thing to do. In the thread where this started it was brought up that you'll get a faster rate of descent by pointing the nose down and accelerate to Vno, the yellow arc. That makes sense, especially if it's a fire and you want to blow it out. I'm trying to figure out what is going to give you the mostest feets per minute descent. Only thing I ever learned about the yellow arc is stay outta it unless it's smooth out and the times I've been in it are with power in a gradual descent to get home quicker. Let's start with a C172. What gives you max 'rate' of descent.
 
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You can also perform an extreme slip if you want to keep the airspeed manageable. That would work better in turbulence, methinks. I routinely see 1000 fpm descent rate turning base to final in the Luscombe, and that's coordinated flight at best glide speed, so a descending turn at idle would probably provide max descent rate.
 
Whatever the POH says. Since the 172S POH doesn’t have a procedure for an emergency descent so I’ve always just taught students to pitch for Vne and execute 30 degree banks to keep a positive load on the aircraft.
 
In the airlines the biggie is rapid or explosive decompression.
 
I love when people claim things are new. I had to do an emergency descent for my commercial check ride 15+ years ago.
We discussed Vfe vs Vne descents in training. Vne if you're on fire is one possibility but when you get down near the ground you're still at Vne. Now what?

A C172 with full flaps at Vfe and spiraling 30-45 degrees comes down REAL quick. Quite surprising actually.

Descents in the yellow arc? My instructors exact words were "this airplane has failed you. It's trying to kill you right now. You owe it nothing."
 
aftCG said:
I love when people claim things are new. I had to do an emergency descent for my commercial check ride 15+ years ago.
We discussed Vfe vs Vne descents in training. Vne if you're on fire is one possibility but when you get down near the ground you're still at Vne. Now what?

A C172 with full flaps at Vfe and spiraling 30-45 degrees comes down REAL quick. Quite surprising actually.

Descents in the yellow arc? My instructors exact words were "this airplane has failed you. It's trying to kill you right now. You owe it nothing."
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Hmm. I did commercial in 1978. Probably did it but don't remember. It is new for PPL. Yeah, the descending at Vne is something you need to deal with when you get down unless your intent is to just plain crash instead of land or a survivable crash landing. I'm still trying to find out if Vno/Vne clean, gives you more feet per minute than Vfe dirty. If it does, but it's not much, you could loose what you had gained on the way down when getting configured to crash/land at a reasonable speed.
 
mscard88 said:
Or one of the two pilots have bad gas. Hell, or both of 'em! :dunno:
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That stuff is lighter than air which ain't helpin things any. Not to mention the fire danger. Don't be flippin none of them sparky ol' switches when the crowd in the cabin starts doin a 'Blazin Saddles' campfire scene reenactment.
 
aftCG said:
Descents in the yellow arc? My instructors exact words were "this airplane has failed you. It's trying to kill you right now. You owe it nothing."
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In real life, yes. But that is no reason to exceed the operating limits of the airplane during a simulation. Just as you wouldn't pull the mixture to idle cut-off to simulate an engine failure.
 
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dmspilot said:
In real life, yes. But that is no reason to exceed the operating limits of the airplane during a simulation. Just as you wouldn't pull the mixture to idle cut-off to simulate an engine failure.
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Ok. Let's forget Vne and stick with Vno. What are the 'numbers.' How many more FPM do you get at Vno clean than Vfe dirty?
 
It's funny, these discussions remain either theoretical or "I do/I've done X and that's the best".

One of us could rent a plane or pull the ol bird out of the hangar and give it a trial and report back on time til touchdown. My excuse? I'm too busy, or too lazy, or the next time I'm just boring holes in the sky I'll forget.

So to add to my hypocrisy: I learned both spirals and slips. I think slips just give me better awareness of my surroundings and I can multi-task better, hence a better chance of survival (whether I need the precious extra time or not, whereas I lose where I am specially relative to cardinal directions when I'm spiraling, if I take my attention away for a sec or two). But that's just me.

Besides, if I'm gonna go, slips are more fun, spirals suck. So there.
 
I deploy the speed brakes and can do >2500fpm. Not sure how much more than that, 'cause I've never looked at the tablet's altitude display and I think my VSI only goes that high. :)
 
Kritchlow said:
In the airlines the biggie is rapid or explosive decompression.
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Fire is a biggie for everyone.

No one scheme is going to work for all aircraft or all situations.

The original Commercial standards called it a "steep spiral" but even the FAA had to concede that might not be the best maneuver. The first question is "emergency descent" to what. It's different if you're trying to get down below 8000' because you've lost pressurization than if you're going to have to land directly out of the descent.

In the Navion I can get a pretty healthy FPM descent by getting dirty ASAP even though it takes slowing down to a pretty low speed to get the gear and flaps out. The good side is I can land directly out of it.
 
If I'm on fire Vne is just a nice number. The nose is getting pointed down. Actually, I've read accounts of guys who've blown past Vne (easy to do in my aircraft) and the planes are still flying. But yeah, if its anything else, slow down, dirty up, and the spiral isn't a bad idea at all. If the emergency is pax related I'll try to be nice to the airplane. If its an airplane malfunction that's causing the emergency I might be a little less so.

This is a really good thread, something I really hadn't thought through before. Thanks.
 
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flyingron said:
Fire is a biggie for everyone.

No one scheme is going to work for all aircraft or all situations.

The original Commercial standards called it a "steep spiral" but even the FAA had to concede that might not be the best maneuver. The first question is "emergency descent" to what. It's different if you're trying to get down below 8000' because you've lost pressurization than if you're going to have to land directly out of the descent.

In the Navion I can get a pretty healthy FPM descent by getting dirty ASAP even though it takes slowing down to a pretty low speed to get the gear and flaps out. The good side is I can land directly out of it.
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Yeah. If it's a 'I gotta get on the ground now' situation, you need to get to a reasonable speed to land at. Hopefully it's to an airport, but may not be. If it's a fire, there's a good argument for trying to blow it out with a Vno-Vne descent. If it's not a fire, then maybe reducing from cruise to Vfe 'up there' rather than from Vno-Vne 'down here' may be the better way to go even if the yellow arc descent 'clean' gives you a faster rate than top of the white arc gives you 'dirty.' Like @455 Bravo Uniform said, it would probably take some 'test piloting' to get the answer for any particular airplane.

EDIT: I'll volunteer to do it. Who's got an airplane I can borrow?
 
dmspilot said:
But that is no reason to exceed the operating limits of the airplane during a simulation.
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In smooth air there is nothing wrong with going into the yellow arc and making smooth control inputs. The plane handles quite a bit differently at 160 knots vs 100, or 130 vs 200, etc., depending on whatever you fly. I think making an emergency practice seem as real as possible will make you that much better to handle it when the real thing comes and have no surprises.. now I've never actually failed an engine for practice.. I think that stretches things a bit too close to becoming a real emergency but people should be comfortable with how the plane handles throughout its entire operating envelope, and that includes up to Vne (in smooth air)
 
steingar said:
If I'm on fire Vne is just a nice number. The nose is getting pointed down. Actually, I've read accounts of guys who've blown past Vne (easy to do in my aircraft) and the planes are still flying. But yeah, if its anything else, slow down, dirty up, and the spiral isn't a bad idea at all. If the emergency is pax related I'll try to be nice to the airplane. If its an airplane malfunction that's causing the emergency I might be a little less so.
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what is your aircraft?
 
luvflyin said:
what is your aircraft?
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My aircraft in a '62 Mooney M20c, and it flies in the yellow arc at 75% power at anything over 5k feet. If descending with any power it's nearly impossible to stay out of the yellow arc.
 
Tantalum said:
In smooth air there is nothing wrong with going into the yellow arc and making smooth control inputs. The plane handles quite a bit differently at 160 knots vs 100, or 130 vs 200, etc., depending on whatever you fly. I think making an emergency practice seem as real as possible will make you that much better to handle it when the real thing comes and have no surprises.. now I've never actually failed an engine for practice.. I think that stretches things a bit too close to becoming a real emergency but people should be comfortable with how the plane handles throughout its entire operating envelope, and that includes up to Vne (in smooth air)
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Good point. Getting into part a of the 'envelope' you've never been in before may not be such a great idea. Especially if it only gains you a few seconds.
 
steingar said:
My aircraft in a '62 Mooney M20c, and it flies in the yellow arc at 75% power at anything over 5k feet. If descending with any power it's nearly impossible to stay out of the yellow arc.
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What's your gut feeling. In your slippery ol' Mooney, say at about 8000 AGL, no fire but you need on the ground ASAP. How would you do it. What is Vfe and Vlo for a M20c
 
Experimented in a C152. The timing was started when the decision to make an emergency descent was made. The timing was stopped after level-off and slowing to landing approach speed (60 knots).

Time to lose 1500 feet:
With flaps: 80 seconds
Without flaps: 60 seconds

The difference would only increase at higher altitudes. Yeah a Mooney might be different but the people who have been practicing emergency descents with flaps were flying Cessnas.
 
steingar said:
Actually, I've read accounts of guys who've blown past Vne (easy to do in my aircraft) and the planes are still flying.
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I could be wrong but I believe part 23 certification does give you some safety buffer. The plane will not disintegrate if it nudges past Vne. Someone correct me if I'm wrong but my understanding was that Vne was set at 90% of Vd, the max design diving speed, and must be at least 1.4 times Vno. So if Vno is 127 knots for a 172 then that means Vd is close to 180 knots... which is comfortably faster than Vne of 160 knots, which is incidentally about 90% of Vd 180 knots (mental math, someone with a calculator can confirm). Further, I think the Vne being 10% of Vd is based on an actual demonstrated test flight, so if the designer say 190 knots but the test flight only took it to 180 knots then Vne will be 90% of the 180 knots

So "theoretically" you could "blow past" the Vne of 160 knots and still be within the design parameters of the airplane. NOT advocating that, but per the certification standards that must be true
 
Mistake Not... said:
I deploy the speed brakes and can do >2500fpm. Not sure how much more than that, 'cause I've never looked at the tablet's altitude display and I think my VSI only goes that high. :)
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What do you fly? Is it a small plane like a Mooney,Bonanza,Centurion etc with speed brakes?
 
dmspilot said:
Time to lose 1500 feet:
With flaps: 80 seconds
Without flaps: 60 seconds
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That actually makes sense to me.. but I wonder what the distance over ground would be? Perhaps even though the no flap descent is faster in time, the actual distance covered is greater. That might explain why "gut" tells you to descend with flaps since you are used to using flaps in the pattern to lose altitude in a short distance (like if you are too high on approach). But if all you want to do is lose altitude pointing the nose down and going fast seems to make sense. In the Cirrus the emergency descents were no flaps, at least when I was taught.
 
dmspilot said:
Experimented in a C152. The timing was started when the decision to make an emergency descent was made. The timing was stopped after level-off and slowing to landing approach speed (60 knots).

Time to lose 1500 feet:
With flaps: 80 seconds
Without flaps: 60 seconds

The difference would only increase at higher altitudes. Yeah a Mooney might be different but the people who have been practicing emergency descents with flaps were flying Cessnas.
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The 'without flaps,' was that at Vno?
 
Tantalum said:
That actually makes sense to me.. but I wonder what the distance over ground would be? Perhaps even though the no flap descent is faster in time, the actual distance covered is greater. That might explain why "gut" tells you to descend with flaps since you are used to using flaps in the pattern to lose altitude in a short distance (like if you are too high on approach). But if all you want to do is lose altitude pointing the nose down and going fast seems to make sense. In the Cirrus the emergency descents were no flaps, at least when I was taught.
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Yes that’s how we teach it. Cirrus POH says to descend clean at Vne or Vno if we expect significant turbulence.
 
Tantalum said:
That actually makes sense to me.. but I wonder what the distance over ground would be? Perhaps even though the no flap descent is faster in time, the actual distance covered is greater. That might explain why "gut" tells you to descend with flaps since you are used to using flaps in the pattern to lose altitude in a short distance (like if you are too high on approach). But if all you want to do is lose altitude pointing the nose down and going fast seems to make sense. In the Cirrus the emergency descents were no flaps, at least when I was taught.
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My gut doesn't tell me that. It tells me that slowing down and putting the flaps down will take longer and the goal of an emergency descent is to descend as quickly as possible.
 
One benefit of Vfe I think is when you level off to land you're already configured w/ flaps and can slow quicker. So I'm wondering that time gained of being configured at Vfe would cancel out the time of Vno, while quicker downhill, which would will require a bit more time to slow and configure for landing. Guess I need to make up a 5x7 card w/ different configurations and fly it. Thoughts?
 
dmspilot said:
Yes.
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I'm starting to get my head wrapped around the Vno clean descent and dirtying it up 'down there' for a C172. That 20 seconds difference in just 1500 feet is significant. That's a minute at 4500 feet and it should take less than that to bleed off the airspeed and get dirty 'down there.' I have a Flight Review coming up in a couple months. I'm going to find a CFI who wants to play with this and find out.
 
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mscard88 said:
One benefit of Vfe I think is when you level off to land you're already configured w/ flaps and can slow quicker. So I'm wondering that time gained of being configured at Vfe would cancel out the time of Vno, while quicker downhill, which would will require a bit more time to slow and configure for landing. Guess I need to make up a 5x7 card w/ different configurations and fly it. Thoughts?
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I wonder if the time it takes to initially get configured with full flaps and start the descent would be the same as immediately starting a Vne descent, then configuring at the level off.
 
jordane93 said:
I wonder if the time it takes to initially get configured with full flaps and start the descent would be the same as immediately starting a Vne descent, then configuring at the level off.
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Good point.
 
I may be thinking about this wrong, but we're trying for the highest sustainable descent rate, right? Whatever IAS and config gives us that, correct?

Or are there other issues that factor in?
 
jordane93 said:
I wonder if the time it takes to initially get configured with full flaps and start the descent would be the same as immediately starting a Vne descent, then configuring at the level off.
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Wouldn't you start the steep turn and descent while slowing to flap speed though?
 
Mistake Not... said:
I may be thinking about this wrong, but we're trying for the highest sustainable descent rate, right? Whatever IAS and config gives us that, correct?

Or are there other issues that factor in?
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Yes. There's the part about getting out of the airplane. If the descent rate is at Vne you can't hop out nearly as fast when you arrive near the ground.

You can't land on a soccer field at 200mph

See, in the spiral I am looking down at my potential landing spot. I can hopefully deduce wind direction and choose how I want to enter while they're are still a few coils in the spiral.
 
Do a clean high speed descent, note rate.
Do a dirty below flap speed descent(with slip? without? or both?), note rate

compare rates, problem solved?
The spiral will affect either method similarly no? So the comparison should hold up. For the Vne descent, factor in some time to slow after level off at the bottom maybe?

excluding the reason for the descent of course, if its a fire, POH may call for the higher speed
 
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