Emergency descent question

livitup

livitup

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livitup
I was Reading the January edition of AOPA Flight Traning, Which has an article about emergency descent being added to the PTS for the private checkride. The article gives a generic method, if there's nothing specific in the POH about emergency decents. They say "flaps and gear should be extended as recommended by the manufacturer". Later in the article they talk about airspeed, and remind you to of course never exceed vNE, but also to watch for vFE if the flaps are out.

So here's the question. In an emergency descent is it better to descend at a rate that's between vFE and vNE, without flaps, or stay under vFE with flaps? I realize that a faster airspeed does not indicate a faster descent per se, but the more nosedown attitude you have, the more airspeed you're going to pick up.

Or would the descent rate be about the same, in feet per minute, At vFE with the flaps extended as it would be at vNE with the flaps in? Or is this question impossible to answer without knowing what plane were talking about?
 
livitup said:
I was Reading the January edition of AOPA Flight Traning, Which has an article about emergency descent being added to the PTS for the private checkride. The article gives a generic method, if there's nothing specific in the POH about emergency decents. They say "flaps and gear should be extended as recommended by the manufacturer". Later in the article they talk about airspeed, and remind you to of course never exceed vNE, but also to watch for vFE if the flaps are out.

So here's the question. In an emergency descent is it better to descend at a rate that's between vFE and vNE, without flaps, or stay under vFE with flaps? I realize that a faster airspeed does not indicate a faster descent per se, but the more nosedown attitude you have, the more airspeed you're going to pick up.

Or would the descent rate be about the same, in feet per minute, At vFE with the flaps extended as it would be at vNE with the flaps in? Or is this question impossible to answer without knowing what plane were talking about?
Click to expand...

Depends on the airplane.

Sent from my SCH-I200 using Tapatalk 2
 
Emer descent has more to do with vertical speed than IAS. As in how long until I'm on the ground watching it burn from a safe distance? Accordingly, the descent configuration and profile (wings level vs banked) will vary according to the plane and the POH.
 
Lets say there was a real fire in the cockpit, whats the issue with passing vNE just for a few seconds so you get get to the ground asap?
 
MultiMediaWill said:
Lets say there was a real fire in the cockpit, whats the issue with passing vNE just for a few seconds so you get get to the ground asap?
Click to expand...



You would have to ask the test pilot that.... Not us...

Maybe the flaps fall off? Maybe the wings?
 
Depends how you do it, and whether you want to be sure you get on the ground rather than into it.

MultiMediaWill said:
Lets say there was a real fire in the cockpit, whats the issue with passing vNE just for a few seconds so you get get to the ground asap?
Click to expand...
 
I've seen both done in the Tecnam Eaglet I fly, and the no flaps Vne 45-60 degree bank method works significantly better than the 45-60 degree bank at Vfe with flaps extended. I know this because my instructor taught me the Vne method, which my examiner liked, but he asked if he could try out the way the FAA's airplane flying handbook says it should be done--the Vfe method. I pegged the VSI with the Vne method, but he could only get roughly 1200 fpm with Vfe method.
 
jpower said:
I've seen both done in the Tecnam Eaglet I fly, and the no flaps Vne 45-60 degree bank method works significantly better than the 45-60 degree bank at Vfe with flaps extended. I know this because my instructor taught me the Vne method, which my examiner liked, but he asked if he could try out the way the FAA's airplane flying handbook says it should be done--the Vfe method. I pegged the VSI with the Vne method, but he could only get roughly 1200 fpm with Vfe method.
Click to expand...

Did either test end with a full stop landing?

One method leaves you at say 10 feet AGL at Vne and the other leaves you at 10AGL at Vfe. For both, you still need to slow down, land, and stop.

The plane will reach a reasonable touchdown speed sooner if you start this process at Vfe with the flaps out compared to reaching 10AGL at Vne clean.

I don't know if the total time from initiating the emergency descent to exiting the airplane would be greater with one method or the other. Seems like it would depend on a lot of variables, including at what altitude you initiated the procedure. So... "it depends..."

-Skip
 
Skip Miller said:
Did either test end with a full stop landing?

One method leaves you at say 10 feet AGL at Vne and the other leaves you at 10AGL at Vfe. For both, you still need to slow down, land, and stop.

The plane will reach a reasonable touchdown speed sooner if you start this process at Vfe with the flaps out compared to reaching 10AGL at Vne clean.

I don't know if the total time from initiating the emergency descent to exiting the airplane would be greater with one method or the other. Seems like it would depend on a lot of variables, including at what altitude you initiated the procedure. So... "it depends..."

-Skip
Click to expand...

Yeah, it depends how high you are. If you're not that far from the ground, Vfe is better. But if you're up cruising at 8500 ft, the Vne method is better. Question is, where is the cutoff? That I don't know. But I do know that if you're descending at 1200 fpm from 8500 ft AGL, it will take you roughly 7 minutes to descend to ground level. If you're descending at 2000 fpm (and that's I'm sure on the slow side) it'll take just over 4 minutes. Slowing from Vne to something reasonable should not take 3 minutes.
 
Skip Miller said:
Did either test end with a full stop landing?

One method leaves you at say 10 feet AGL at Vne and the other leaves you at 10AGL at Vfe. For both, you still need to slow down, land, and stop.

The plane will reach a reasonable touchdown speed sooner if you start this process at Vfe with the flaps out compared to reaching 10AGL at Vne clean.

I don't know if the total time from initiating the emergency descent to exiting the airplane would be greater with one method or the other. Seems like it would depend on a lot of variables, including at what altitude you initiated the procedure. So... "it depends..."

-Skip
Click to expand...

That is why you don't aim for the airport, but 3 miles out. Then you put the gear out at Vne, (rip off the gear doors is Okay) slow to Vfe, drop all flaps, land, parking brake, shut down, egress.

It is the most fun I ever had at FlightSafety.
 
livitup said:
In an emergency descent is it better to descend at a rate that's between vFE and vNE, without flaps, or stay under vFE with flaps?
Click to expand...
The answer lies in the POH for that model airplane because there there are too many variables for a generic answer.
 
Ron Levy said:
The answer lies in the POH for that model airplane because there there are too many variables for a generic answer.
Click to expand...

Acknowledged. I've not read more than a couple POH's, so I don't have a lot of experience, but the AOPA article indicated it was a crapshoot for there to be a procedure or checklist on any given plane. The POH for my school's 172SP does not have an emergency descent procedure. I checked the engine fire checklist, thinking that engine fire would be a good reason to want to be parking it quick, and there's this:
6. Airspeed - 100 KIAS (If fire is not extinguished, increase glide speed to find an airspeed, within airspeed limitations,
which will provide an incombustible mixture)
7. Forced Landing - EXECUTE Refer to EMERGENCY
LANDING WITHOUT ENGINE POWER
Click to expand...
Not super helpful in answering this question.
 
Skip Miller said:
Did either test end with a full stop landing?

One method leaves you at say 10 feet AGL at Vne and the other leaves you at 10AGL at Vfe. For both, you still need to slow down, land, and stop.
Click to expand...

I presume that any emergency descent to a full stop would involve slowing to a reasonable landing speed (with flaps, if possible) before contact with the ground. It won't do much good to be on the ground if the plane lawn darts.
 
Ron Levy said:
The answer lies in the POH for that model airplane because there there are too many variables for a generic answer.
Click to expand...
I have to go with Ron on this one, and if the POH is not helpful for your model then maybe it is time for an experiment to prove what works best for your model.
 
Also, it isn't always about rate of descent but about radius of turn. Spiraling down through a hole in the overcast, you want as small a radius of turn as possible.
 
nosehair said:
Also, it isn't always about rate of descent but about radius of turn. Spiraling down through a hole in the overcast, you want as small a radius of turn as possible.
Click to expand...

Well if that's you're criteria then just spin it.
 
bflynn said:
Does this help?
http://www.youtube.com/watch?v=nQcOUSrG4lc

How about this one?
http://flash.aopa.org/asf/pilotstories/fireinthecockpit/
Click to expand...

Not really... The King video talks about 100 knots, which is in my POH as the best speed to extinguish a fire, but that's not what the PTS is asking in this case, it's asking for emergency descent. I haven't been able to find anywhere if the 172's best decent rate is at 100 knots, or if that's just some magic fire-fighting-airflow-inducing speed.

I guess the answer is, if it's not in the POH, to test it out in your plane, and for the check ride, to ask the DPE if they prefer the vFE or Vne method.
 
livitup said:
I haven't been able to find anywhere if the 172's best decent rate is at 100 knots, or if that's just some magic fire-fighting-airflow-inducing speed.
Click to expand...

Well, the best descent rate is whatever you get pointing straight down...but I'm not sure you want that :)
 
I noticed that the latest issue of AOPA Flight Training had two articles about emergency descents in it!
 
When you get to bigger airplanes you find there are two types of emergency descent too. High Speed and Low Speed. Think structural failure for low speed and lost cabin pressure for the high speed.

There was a BA flight where the captains window blew out sucking the Captain halfway out of the plane. Explosive decompression and the FO elected to do a high speed Emergency Descent. Poor choice IMO. With the structural Damage and a Human hanging out if the plane Low Speed would have been my choice.

I would imagine the choice between dirtying up and flying Vfe or staying clean and flying Vne has to do with how close Vfe is to Vne. If it a 200 kt split and the plane has spoilers then Vne may be the best descent choice. If there's no split or it's only 30 kts or so then getting all that extra drag may help get a better descent rate.

It's all about the descent rate and starting altitude doesn't really matter as slowing to Vref with no power takes no time...or at least inconsequential amount of time compared to getting down (the point of the ED).

I think the POHs aim to maximize the descent rate in selecting configuration.
 
Captain said:
When you get to bigger airplanes you find there are two types of emergency descent too. High Speed and Low Speed. Think structural failure for low speed and lost cabin pressure for the high speed.

There was a BA flight where the captains window blew out sucking the Captain halfway out of the plane. Explosive decompression and the FO elected to do a high speed Emergency Descent. Poor choice IMO. With the structural Damage and a Human hanging out if the plane Low Speed would have been my choice.

I would imagine the choice between dirtying up and flying Vfe or staying clean and flying Vne has to do with how close Vfe is to Vne. If it a 200 kt split and the plane has spoilers then Vne may be the best descent choice. If there's no split or it's only 30 kts or so then getting all that extra drag may help get a better descent rate.

It's all about the descent rate and starting altitude doesn't really matter as slowing to Vref with no power takes no time...or at least inconsequential amount of time compared to getting down (the point of the ED).

I think the POHs aim to maximize the descent rate in selecting configuration.
Click to expand...
Bob Schmelzer, a DPE out of KDPA and a 777 instructor pilot, wrote one of the articles in AOPA Flight Training this month, and he too drew the distinction between the two types of emergency descent.
 
gprellwitz said:
Bob Schmelzer, a DPE out of KDPA and a 777 instructor pilot, wrote one of the articles in AOPA Flight Training this month, and he too drew the distinction between the two types of emergency descent.
Click to expand...

link?
 
Captain said:
Poor choice IMO. With the structural Damage and a Human hanging out if the plane Low Speed would have been my choice.
Click to expand...

Not unless the FO was wanting to move up a number!
 
livitup said:
I was Reading the January edition of AOPA Flight Traning, Which has an article about emergency descent being added to the PTS for the private checkride. The article gives a generic method, if there's nothing specific in the POH about emergency decents. They say "flaps and gear should be extended as recommended by the manufacturer". Later in the article they talk about airspeed, and remind you to of course never exceed vNE, but also to watch for vFE if the flaps are out.

So here's the question. In an emergency descent is it better to descend at a rate that's between vFE and vNE, without flaps, or stay under vFE with flaps? I realize that a faster airspeed does not indicate a faster descent per se, but the more nosedown attitude you have, the more airspeed you're going to pick up.

Or would the descent rate be about the same, in feet per minute, At vFE with the flaps extended as it would be at vNE with the flaps in? Or is this question impossible to answer without knowing what plane were talking about?
Click to expand...

My preferred method was to bank, yank to bleed off airspeed, pop full flaps once within VFE and do a forward slip at the limit of VFE. Most spam cans drop like bricks with that flight profile.

The key is to spoil lift and not build up excess speed that you must later bleed off..
 
I instruct in Bonanzas. The emergency descent procedure varies by specific model. Earlier models have lower flap and gear speeds. For later models, the flaps have an approach detent setting, while the earlier aircraft have continuous position flaps without any detent other than up or down. For my particular model, a 68 V35A, the flaps are not used in the emergency descent as there is no approach detent. Power is set to idle, gear lowered, prop full forward, pitch for descent at 145 KIAS (Maximum gear extended speed). The deck angle is wild. Pilot's are generally unwilling to pitch the nose low enough to obtain the desired speed when demonstrating the maneuver and have to be encouraged to lower the nose further. I have a cue that I use that tells me when I am at the right deck angle, the seat rocks forward on the rails when I am at the desired deck angle as the CG of the pilot goes over center. Rate of descent is close to 6000 FPM, so from 6000 AGL, I can be in the flare one minute later.
 
Doggtyred said:
My preferred method was to bank, yank to bleed off airspeed, pop full flaps once within VFE and do a forward slip at the limit of VFE. Most spam cans drop like bricks with that flight profile.

The key is to spoil lift and not build up excess speed that you must later bleed off..
Click to expand...

Disagree. As has already been mentioned, it depends on your altitude above your landing site. If you're at pattern altitude, then I'd use your method. If higher, your method will give far from the fastest vertical descent rate.

Regarding bleeding off excess speed, a 4.4G power-off steep turn will get you from Vne to 1.3Vso in literally a few seconds. If you're much higher than pattern altitude, a Vne power-off max G banked turn will get you down a whole lot faster than the way you describe. Even with the few seconds you spend bleeding speed, you'll still come out far ahead. Again, if you're already very low, then you might as well fly nearly a normal slipped approach.
 
RoscoeT said:
Regarding bleeding off excess speed, a 4.4G power-off steep turn will get you from Vne to 1.3Vso in literally a few seconds. If you're much higher than pattern altitude, a Vne power-off max G banked turn will get you down a whole lot faster than the way you describe. Even with the few seconds you spend bleeding speed, you'll still come out far ahead. Again, if you're already very low, then you might as well fly nearly a normal slipped approach.
Click to expand...

Why would you pull beyond the Normal Category G limit in a spamcan that's 30+ years old?
 
denverpilot said:
Why would you pull beyond the Normal Category G limit in a spamcan that's 30+ years old?
Click to expand...

The common spam cans (152/172/Cherokee) are certificated in the normal and utility categories. Utility g-limit is 4.4. Normal is 3.8G. Even for airplanes only in the normal category, are you going to worry about half a G in an emergency descent?
 
RoscoeT said:
The common spam cans (152/172/Cherokee) are certificated in the normal and utility categories. Utility g-limit is 4.4. Normal is 3.8G. Even for airplanes only in the normal category, are you going to worry about half a G in an emergency descent?
Click to expand...

Depends on the specific airplane.

How much faster in seconds will you be on the ground pulling 4.4 vs 3 or so? I suspect it's not a significant difference.

None of the new Cessnas have been Utility certified for over a decade now, as one significant example.
 
It's often the case that the response to one emergency creates another. I too would be very hesitant to pull 3 or 4 Gs simply to bleed speed. To miss the mountain? Sure. To slow down? Nah. I can spend an extra 3 seconds to slow down.


Besides, if going off airport to land my number one priority is to be stabilized.
 
denverpilot said:
How much faster in seconds will you be on the ground pulling 4.4 vs 3 or so? I suspect it's not a significant difference.
Click to expand...

50% more induced drag is insignificant? And there is nothing wrong with putting the max Gs on an airplane. They are designed for it. And it will not break or cause problems if you go slightly over. There is a 50% margin before airframe deformation occurs. Not saying that you should ignore the g-limits, but going slightly over one time in an emergency won't hurt anything. You just don't want to do it continually. But pulling to the max g-load either 4.4 or 3.8 is not a problem. The designers allow for that to be done on every flight. And .5G isn't going to make any difference unless you're near the ultimate load failure point (6.6G in a utility category spamcan).
 
Last edited:
denverpilot said:
Why would you pull beyond the Normal Category G limit in a spamcan that's 30+ years old?
Click to expand...

Well, I'm not exactly sure if they're designed with the same safety factor as the bigger airplanes, but if they are, they should withstand up to 6.6 gs without snapping. 4.4 seems pretty all right to me...it's hard to imagine adding another 2 gs without noticing it.
 
An emergency descent would be a nose down, max safe airspeed,
minimum power configuration. While there may be a short transit
through some G change, I'm not seeing where an airspeed stable
decent would cause any additional G loading.
 
RoscoeT said:
50% more induced drag is insignificant? And there is nothing wrong with putting the max Gs on an airplane. They are designed for it. And it will not break or cause problems if you go slightly over. There is a 50% margin before airframe deformation occurs. Not saying that you should ignore the g-limits, but going slightly over one time in an emergency won't hurt anything. You just don't want to do it continually. But pulling to the max g-load either 4.4 or 3.8 is not a problem. The designers allow for that to be done on every flight. And .5G isn't going to make any difference unless you're near the ultimate load failure point (6.6G in a utility category spamcan).
Click to expand...

How many old fart, 50+, out of shape pilots you think are going to be fine going straight to 4.4G with no experience doing so?

We can keep coming up with bad reasons for this as GENERAL advice, all day long.

Not recommended.
 
turbo_jjr said:
An emergency descent would be a nose down, max safe airspeed,
minimum power configuration. While there may be a short transit
through some G change, I'm not seeing where an airspeed stable
decent would cause any additional G loading.
Click to expand...

Agreed...

It is the pull up at the bottom of the decent that sheds the wings.:yes::hairraise:
 
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