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How Are Emergency Descents Conducted?  
User currently offlineJackbr From Australia, joined Dec 2009, 665 posts, RR: 0
Posted (3 years 4 months 2 weeks 1 day 10 hours ago) and read 7366 times:

What are the general procedures for undertaking an emergency descent on an airliner?

Apologies if this question is way too vague, my technical operations knowledge is limited

38 replies: All unread, showing first 25:
 
User currently offlinewilco737 From Greenland, joined Jun 2004, 8968 posts, RR: 76
Reply 1, posted (3 years 4 months 2 weeks 1 day 10 hours ago) and read 7376 times:
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Quoting Jackbr (Thread starter):
What are the general procedures for undertaking an emergency descent on an airliner?

Basically, get down ASAP, thrust levers idle, speedbrake extend and with Vmo/ Mmo down to roughly 10-14,000 feet.


wilco737
  



It it's not Boeing, I am not going.
User currently offlineetherealsky From United States of America, joined Apr 2010, 328 posts, RR: 0
Reply 2, posted (3 years 4 months 2 weeks 1 day 9 hours ago) and read 7360 times:

Quoting wilco737 (Reply 1):

Gear/flaps used as well?



"And that's why you always leave a note..."
User currently offlineRendezvous From New Zealand, joined May 2001, 515 posts, RR: 0
Reply 3, posted (3 years 4 months 2 weeks 1 day 9 hours ago) and read 7341 times:

You'd have to slow down a fair bit to use flap - that takes time.

User currently offlinezeke From Hong Kong, joined Dec 2006, 8865 posts, RR: 75
Reply 4, posted (3 years 4 months 2 weeks 1 day 7 hours ago) and read 7319 times:

Quoting Jackbr (Thread starter):
What are the general procedures for undertaking an emergency descent on an airliner?

Oxygen masks on
Establish communications with the other pilot

Start of loop

Select heading and commence a turn off the airway (as traffic maybe below)
Select a lower altitude and commence a descent (this should command the autothrust/throttle to IDLE)
Select the current speed/mach
Check speed, check autopilot/autothrust modes, check commanded thrust level
Select full speed brake whilst monitoring speed
Both thrust levers back to IDLE if the thrust is not at IDLE

The monitoring pilot sits on their hands and monitors these vital actions to ensure the PF gets the aircraft established in the emergency descent safely.

The PF repeats the first loop

Heading okay ? where is traffic/terrain ?
Altitude okay, what height is the terrain ?
Speed, was the aircraft damaged, if it was damaged (e.g. explosive loss of a cargo door) you would keep the indicated speed at the time of the explosive decompression, otherwise, select Vmo/Mmo
Check speed, check autopilot/autothrust modes, check commanded thrust level

The pilot monitoring at the same time as the PF make the second loop
Transmits a mayday call
Turns the engine igniters on
Emergency code on transponder
No smoking/seat belt signs on
Engine anti-ice if required
Lights on
Works through the electronic and/or QRH checklist

Quoting etherealsky (Reply 2):

Gear/flaps used as well?

Gear maybe used in the case of damage, as it will increase drag, normally gear and flap cannot be selected above FL200. Flap would not be used.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlinewilco737 From Greenland, joined Jun 2004, 8968 posts, RR: 76
Reply 5, posted (3 years 4 months 2 weeks 1 day 6 hours ago) and read 7268 times:
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Quoting etherealsky (Reply 2):
Gear/flaps used as well?

Nope, All airlines I worked at: Gear and flaps up! The speed needs to be reduced significantly to lower gear and flaps and then you cannot descent with Vmo anymore, you need to use Vle, or the max flap placard speed...
I think only about the 744 where flaps 1 to flaps 5 can take up to 30 seconds. In 30 seconds I have already descended 2000-2500 feet in clean configuration with speed brake extended and Mmo/ Vmo.

Quoting zeke (Reply 4):
normally gear and flap cannot be selected above FL200

They can be used, but it has never been officially certified to use them above 20,000 feet, as there is no normal condition where you need it.

wilco737
  



It it's not Boeing, I am not going.
User currently offlinezeke From Hong Kong, joined Dec 2006, 8865 posts, RR: 75
Reply 6, posted (3 years 4 months 2 weeks 1 day 3 hours ago) and read 7166 times:

Quoting wilco737 (Reply 5):
They can be used, but it has never been officially certified to use them above 20,000 feet, as there is no normal condition where you need it.

I would not use the word "can", if something is not permitted as it is an aircraft limit, it cannot normally be used.

It could only be used by the Captain if they had the view that the limit has be intentionally exceeded under their emergency authority for the safe outcome of the flight. Otherwise their licence could be revoked, or in worst case, end up in jail for wilful negligence.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offline330guy From Ireland, joined Nov 2010, 453 posts, RR: 2
Reply 7, posted (3 years 4 months 2 weeks 1 day 1 hour ago) and read 7128 times:

I was on a flight a few years ago where we had an emergancy descent over Rotterdam, we were in a Gulf Air A330 going from DUB-BAH... There was a sudden jolt of turbulance that hit the aircraft, It seemed to take forever but in reality it was maybe only 10secs or less before the aircraft pitched down (you all mention throttles to idle but im certian the throttles were opened or power atleast significantly increased) a few moments later (about a minute) the captian came on and apologised for the sudden madness and advised we had hit some extremly strong turbulance and he had to commence an emergancy descent. We descended 7000ft as stated by the captain.
It was a thrilling ride to say the least but next time I think i'd like to know about it before it happens 



Aircraft flown: a300/10/20/21/30/40, b727/37/47/57/67/, DC9, MD80-90, l1011, f50, atr42/72, shorts360, pc12
User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Reply 8, posted (3 years 4 months 2 weeks 1 day 1 hour ago) and read 7120 times:

What about using inboard T/Rs on four engine airplanes or maybe the t/r on no. 2 on tri-jets?


"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
User currently offline330guy From Ireland, joined Nov 2010, 453 posts, RR: 2
Reply 9, posted (3 years 4 months 2 weeks 1 day 1 hour ago) and read 7110 times:

Quoting c5load (Reply 8):
What about using inboard T/Rs on four engine airplanes or maybe the t/r on no. 2 on tri-jets?

Is it possible to engage the reversers in flight?? always beleived it was not



Aircraft flown: a300/10/20/21/30/40, b727/37/47/57/67/, DC9, MD80-90, l1011, f50, atr42/72, shorts360, pc12
User currently offlinetravelavnut From Netherlands, joined May 2010, 1586 posts, RR: 7
Reply 10, posted (3 years 4 months 2 weeks 1 day 1 hour ago) and read 7109 times:

Quoting 330guy (Reply 9):
Is it possible to engage the reversers in flight?? always beleived it was not

It was possible for the DC-8 IIRC.



Live From Amsterdam!
User currently onlineANITIX87 From United States of America, joined Mar 2005, 3299 posts, RR: 13
Reply 11, posted (3 years 4 months 2 weeks 1 day ago) and read 7105 times:
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Quoting 330guy (Reply 9):
Is it possible to engage the reversers in flight?? always beleived it was not

Depends on the aircraft. Concorde was designed to use her T/R in-flight to slow down if needed.

What is the typical descent in FPM that one can achieve during an emergency descent? On a related note, what's the typical nose-down angle for maximum emergency descent?

How much time elapses between the PF thinking, "We need to execute an emergency descent" to the moment when maximum descent rate is achieved?

TIS



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User currently offlinePihero From France, joined Jan 2005, 4389 posts, RR: 76
Reply 12, posted (3 years 4 months 2 weeks 23 hours ago) and read 7055 times:
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Zeke has pretty much written everything to know on a modern airplane.
The only addition, may be, would be to consider a higher Mach /Ias for the descent if there is no structure damage.

Quoting zeke (Reply 4):
Gear maybe used in the case of damage, as it will increase drag, normally gear and flap cannot be selected above FL200. Flap would not be used.

The use of the landing gear was a 741 / 2 / 3 SOP, the captain had a choice of whether use them or not. It allowed a slower IAS / Mach, limited to Vle .
The procedure was awkward as it involved all three flight deck personnel being rather busy. It was cancelled on the 744 on some airlines.



Contrail designer
User currently offlinewilco737 From Greenland, joined Jun 2004, 8968 posts, RR: 76
Reply 13, posted (3 years 4 months 2 weeks 23 hours ago) and read 7049 times:
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Quoting zeke (Reply 6):
I would not use the word "can", if something is not permitted as it is an aircraft limit, it cannot normally be used.

Isn't that what I have written? I said, they can be used, but it has never been certified. Basically it is possible. Sure, it is a limitation which has to be observed under normal conditions... But what do I know...

wilco737
  



It it's not Boeing, I am not going.
User currently offline26point2 From United States of America, joined Mar 2010, 810 posts, RR: 0
Reply 14, posted (3 years 4 months 2 weeks 23 hours ago) and read 7034 times:

Many newer bizjets have an Auto Emerg Descent feature. Autopilot and autothrottle commences an emergency descent without any pilot input when cabin altitude reaches +24;000' (?). The GLEX descends to and captures 15,000'. The system good if the pilots are incapacitated. I don't know if airliners have this feature.

User currently offlinePolymerPlane From United States of America, joined May 2006, 991 posts, RR: 3
Reply 15, posted (3 years 4 months 2 weeks 22 hours ago) and read 7010 times:

Quoting zeke (Reply 4):
Select a lower altitude and commence a descent (this should command the autothrust/throttle to IDLE)

Do you select descent rate?



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User currently offlinePihero From France, joined Jan 2005, 4389 posts, RR: 76
Reply 16, posted (3 years 4 months 2 weeks 22 hours ago) and read 7003 times:
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Quoting PolymerPlane (Reply 15):

Do you select descent rate?

No, your descent will be made on :
- idle thrust
- extended speed brakes
- high speed, selected
and all the above will make your descent, i.e your rate of descent, as high as can be.
- to the selected level-off altitude, which is in general FL 100 or MSA if higher.



Contrail designer
User currently offline26point2 From United States of America, joined Mar 2010, 810 posts, RR: 0
Reply 17, posted (3 years 4 months 2 weeks 21 hours ago) and read 6977 times:

Quoting PolymerPlane (Reply 15):
Do you select descent rate?

...the plane needs a vertical mode for vertical guidance, FLCH (FL Change) is used. This mode maintains selected speed. Vmo/Mmo.


User currently offlinewilco737 From Greenland, joined Jun 2004, 8968 posts, RR: 76
Reply 18, posted (3 years 4 months 2 weeks 21 hours ago) and read 6978 times:
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Quoting 26point2 (Reply 17):
FLCH (FL Change

FL CH is the one we use. Then the pitch will be adjusted automatically to maintain Mmo/ Vmo.

wilco737
  



It it's not Boeing, I am not going.
User currently offlinePihero From France, joined Jan 2005, 4389 posts, RR: 76
Reply 19, posted (3 years 4 months 2 weeks 20 hours ago) and read 6938 times:
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Quoting 26point2 (Reply 17):

...the plane needs a vertical mode for vertical guidance, FLCH (FL Change) is used
Quoting wilco737 (Reply 18):

FL CH is the one we use. Then the pitch will be adjusted automatically to maintain Mmo/ Vmo.

That's for the Boeings;
On the 'Bus, no need to select a mode, the procedures above automatically trigger the OPEN DESCent mode, equivalent to the Boeing FL CH on a descent profile.
I did not want to be type specific.



Contrail designer
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 20, posted (3 years 4 months 2 weeks 17 hours ago) and read 6875 times:

Quoting 26point2 (Reply 14):
Many newer bizjets have an Auto Emerg Descent feature. Autopilot and autothrottle commences an emergency descent without any pilot input when cabin altitude reaches 24;000' (?). The GLEX descends to and captures 15,000'. The system good if the pilots are incapacitated. I don't know if airliners have this feature.


The L-1011-500 (and BA -200's) have a system called Recovery Speed Brakes (RSB). At high altitudes and high Mach numbers the Flight Controls Electronic System (FCES) computers reschedule the spoilers so all 12 spoiler panels are active, in lieu of just 10 active panels on aircraft without RSB. RSB allows the crew to fully deploy the spoilers (with the travel limited on some panels) and not worry about high speed buffeting that could be experience on those L-1011's not equipped with RSB's.


User currently onlinevikkyvik From United States of America, joined Jul 2003, 9776 posts, RR: 27
Reply 21, posted (3 years 4 months 2 weeks 14 hours ago) and read 6788 times:
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A few questions:

1.) Speed brake use during emergency descent - are they primarily used as spoilers (kill lift thereby increasing descent) or speed brakes (helping prevent the aircraft from overspeeding)? Obviously it will be a combination, but I'm just wondering which is the primary function in this case.

2.) What sort of deck angle will allow you to maintain Vmo/Mmo on idle thrust?

Quoting wilco737 (Reply 5):
flaps 1 to flaps 5 can take up to 30 seconds

Geez! That's only one step of flap setting, right (i.e. there's no flaps 2, 3, or 4)?

Thanks!



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User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 22, posted (3 years 4 months 2 weeks 12 hours ago) and read 6752 times:

Quoting wilco737 (Reply 5):
Quoting zeke (Reply 4):
normally gear and flap cannot be selected above FL200

They can be used, but it has never been officially certified to use them above 20,000 feet, as there is no normal condition where you need it.

On some aircraft it cannot be used...the AFM limitation is actually coded into the flap actuation logic, so if you move the handle above 20,000' nothing happens.

Quoting ANITIX87 (Reply 11):
What is the typical descent in FPM that one can achieve during an emergency descent? On a related note, what's the typical nose-down angle for maximum emergency descent?

You can get north of 15,000 FPM (briefly) on some more slippery designs during the initial pitch-over to capture speed. Once you catch up to the Mmo line, you can be over 10,000 FPM. Nose-down angle isn't as vigorous as you might think...maybe 15 degrees initially.

Quoting ANITIX87 (Reply 11):
How much time elapses between the PF thinking, "We need to execute an emergency descent" to the moment when maximum descent rate is achieved?

A few seconds...the highest rate of descent is in the initial pitchover to accelerate to Mmo. Once you're on the Mmo/Vmo curve your rate of descent goes down.

Quoting vikkyvik (Reply 21):
1.) Speed brake use during emergency descent - are they primarily used as spoilers (kill lift thereby increasing descent) or speed brakes (helping prevent the aircraft from overspeeding)? Obviously it will be a combination, but I'm just wondering which is the primary function in this case.

Primarily drag...the whole point of the exercise is to shed energy as quickly as possible.

Tom.


User currently offlinewilco737 From Greenland, joined Jun 2004, 8968 posts, RR: 76
Reply 23, posted (3 years 4 months 2 weeks 11 hours ago) and read 6752 times:
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Quoting vikkyvik (Reply 21):
Geez! That's only one step of flap setting, right (i.e. there's no flaps 2, 3, or 4)?

Yes, the first step where the trailing edge flaps come out. Flaps one is only the inboard and midspan leading edge flaps.

wilco737
  



It it's not Boeing, I am not going.
User currently offline26point2 From United States of America, joined Mar 2010, 810 posts, RR: 0
Reply 24, posted (3 years 4 months 2 weeks 7 hours ago) and read 6688 times:

Quoting tdscanuck (Reply 22):
You can get north of 15,000 FPM (briefly) on some more slippery designs

An aircraft's certified maximum altitude is determined by its ability to descend to 10,000' in 4 minutes.


25 Speedbird741 : They would extend in the alternate flap mode correct? Speedbird741
26 lowrider : Having trained both ways in the classic, I can tell you that if you from most altitudes, gear down gets you down to 14000 feet faster, and with a ste
27 Pihero : Yes we're no longer in an emergency descent situation. The oxygen requirements become one of the limiting factors, along with a published escape traj
28 lowrider : Does your company provide these? We are left to our own devices for this.
29 Pihero : Yes. The documents are called "Aid to decision in case of pressurisation failure" and "Oxygen accessibility zones"Sometimes they are quite specific as
30 Crosswind : My aircraft memory items as follows; - Continuous Ignition - ON - Throttles - CLOSED - Speed Brakes - DEPLOY - Pitch - INITIALLY 20 DEGREES NOSE DOWN
31 474218 : Most aircraft spoilers have a "blow down speed". Deploying the spoilers above the "blow down speed" will result in less then full spoiler travel and
32 tdscanuck : I think so, but I haven't actually tried that. Good question, more research required. Tom.
33 vikkyvik : Is a depressurization + engine failure considered too unlikely a situation? What would you do if that happened?
34 glen : The simultaneous failure of one engine and loss of pressurization is also calculated on the ETOPS-analysis and is normally the most restricting scena
35 AJ : My biggest concern would be damage to the airframe that would prohibit retracting the gear again. A bit of a problem mid-Pacific!
36 Post contains links Chamonix : 77W emergency http://videos.tf1.fr/infos/2011/atte...air-france-les-images-6226106.html
37 AJ : Looked more like a 772 to me. I don't get the connection to a depressurisation. This story is about a pilot's incapacitation?
38 Post contains images Pihero : Yes, but you'll have to get used to chamonix's unique way of going all over the place to get answers !
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