Aviation training is often bashed for having a tombstone mentality. We tend to ignore certain shortcomings until an accident or incident instills new religion. Emergency descent training is a prime example of this.
Throughout my private, commercial and ATP courses, I dont remember getting instruction in emergency descents. Yet after the ValuJet, Swiss Air and FedEx accidents-each of which involved fire in flight-every checkride Ive had has included an emergency descent.
Whats the big deal with emergency descents? And is this skill worth your attention? Take one look at the burned wreckage of the FedEx DC-10 at Newburgh, New York in 1996 for your answer. That crew had to get on the ground right now and even at that, they barely escaped as the cockpit filled with choking smoke. Had they delayed descent even a few seconds, the outcome may have been very different.
When and Why?
When would you want to use an emergency descent? Three scenarios come to mind. The first is smoke in the cockpit. Its more common than you might believe in general aviation aircraft. I found 82 smoke-in-the-cockpit accidents in general aviation aircraft in the NTSBs database between 1997 and 1999. Nearly a quarter of those apparently incapacitated the pilot before the aircraft could safely land. This is clearly a situation where seconds count.
Another common scenario is the loss of cabin pressure in a pressurized aircraft, requiring an emergency descent down to normal breathing altitudes. Related to that is the failure of the oxygen system in an unpressurized airplane.
The point of an emergency descent is to get on the ground immediately, albeit with the wings still intact. No one has done this better than the crew of a FedEx DC-10 that experienced smoke in the cargo cabin during high-altitude cruise flight while enroute from Memphis to Boston in September of 1996.
The crew managed to get the aircraft on the ground just as flames chased their hind sides out the cockpit windows. Fire and rescue crews arrived immediately and although they fought the fire for four hours, there was nothing left of the DC-10 but smoking wreckage.
Dont think that this can happen only to heavy metal drivers. In another accident, the crew of a traffic watch aircraft had smoke and flames enter the cockpit as the aircraft was circling just outside of the traffic pattern of a busy southern California airport. The pilot landed downwind immediately and escaped as flames consumed the cockpit. It made for dramatic footage on the evening news.
What To Do
First and foremost, take care of yourself. If the aircraft lost pressurization, don your oxygen mask first. Air carrier pilots are required to demonstrate the ability to rapidly don oxygen masks, with a single hand, within five seconds and without eyeglasses interfering.
If you fly a pressurized aircraft, you should always have readily available access to the mask, the oxygen should be turned on and you should be able to don the mask quickly. Try it from time to time to make sure you can do it. If, during the emergency, you suspect your source of oxygen is contaminated, consider using the emergency back-up, if you have one. If you dont have one, theyre cheap, consisting of a small 10-minute bottle with an attached mask.
Unless circumstances are dire indeed, its best to respect the aircrafts structural envelope by some margin. In the jet transports I fly, the procedure is to reduce the power to idle, extend the spoilers, lower the nose and push the aircraft up to barber pole or red line adjusted for altitude.
It may be uncomfortable pushing the nose over to 20 degrees below the horizon. Its an awfully steep attitude, but thats whats necessary. The altimeter unwinds fast while descending in excess of 6,000 feet per minute, but it will seem an eternity in an emergency. An emergency descent from normal cruise altitude in a jet can take several precious minutes. It will take just as long in a slower airplane at lower altitudes.
General aviation manufacturers vary on their recommendations for quick descents; some are silent on the subject. The Seneca II manual, for instance, recommends closing the throttles, moving the propeller controls full forward-more drag to aid descent-adjusting the mixture control for smooth engine operation and extending the landing gear at 129 KIAS, followed by the recommendation to maintain this speed.
The Beechcraft F33 manual recommends a similar procedure, but with a 154-knot indicated airspeed.
POHs without a recommended emergency descent procedure leave you with two choices: You can choose to descend in the clean configuration-flaps and gear up-with the throttle at idle. Or you can slow down, dirty up and then pick an airspeed out of the hat.
What speed should you choose? Thats difficult to answer if your manual doesnt recommend anything. In theory, a FAR Part 23 aircraft has a small margin from Vd, the maximum diving speed, and this establishes Vne, the red line. The aircraft should be able to withstand diving up to this speed, albeit in smooth air.
The effects of even mild turbulence are worse at higher speeds, inducing high structural loads on the aircraft. If the air is smooth, then diving up to the red line should be safe. If the air is bumpy, then the bottom of the yellow arc/top of the green arc, would be the maximum safe speed for descending. If the air is exceptionally bumpy, maneuvering speed is the best choice. If your aircraft is one of the few equipped with spoilers or speed brakes, deploy them to aid your descent rate.
During get-it-down-now descents, pitch angle will seem to be the steepest youve ever seen, unless youve had aerobatic training. The wind noise will seem extraordinarily loud and yes, it should make you feel uncomfortable because the aircraft wasnt designed to fly at this speed in normal flight.
If you have a fixed-pitch propeller, dont be surprised if you see the propeller RPM screaming beyond the redline. That will occur because the air is driving the propeller, even though the throttle is closed. If you have a constant-speed propeller, the governor will manage propeller pitch to maintain the selected RPM. Setting full flat pitch-prop control forward-will create some drag and aid your rapid descent. But it wont be a dramatic difference.
Dealing with Damage
Now lets assume the case of a window blowing out of your pressurized aircraft and perhaps some structural damage. If you suspect damage to the aircraft, then the low-speed emergency descent is recommended. This involves slowing down to your maximum flaps extended speed and descending with the flaps and gear extended. Once again, youll feel uncomfortable with the pitch angle of the aircraft diving at the Vfe. The pitch attitude will seem abnormally steep with the flaps down.
Several airline training manuals suggest making a 45-degree bank while initiating an emergency descent. Why? It aids in getting the nose of the aircraft pointed downward to hasten the descent without pushing negative Gs and allows a lower pitch without excessive speed. Further, it changes the aircrafts direction.
Remember that many aircraft are flying Victor airways or jet routes, and hence you arent certain if another aircraft is at a lower altitude on your route and you may not have time to ask ATC. By turning off the airway, youre playing the odds that youre turning away from a conflict with traffic below.
While doing your descent, youll have to consider where youre going to land. If the emergency was due to a problem with oxygen or pressurization, getting the aircraft below 10,000 feet is a good goal, unless youre over the Rocky Mountains and in IMC.
Youre safe from the terrain when descending to the MEA, although if you turned off the airway, you cant be certain of the minimum safe altitude. This one is a judgment call. If in doubt, descend straight ahead on the airway to the MEA and worry about conflicting traffic later. In the U.S., there are MEAs above what most of us would consider breathable altitudes but there arent many of these.
If youve had a problem with the aircraft, its prudent to land at a suitable airport to get the problem fixed, then plan the remainder of the flight on the ground in the relative low-stress of a comfortable FBO.
What if your emergency descent was initiated because of smoke? Now your problem is more serious. Bluntly, you need to get out of the airplane as quickly as possible. Like an hour ago. Despite having a fire wall thats designed to keep heat and flame out of the cockpit, the firewall is sufficient only to a point.
From talking with pilots and rescuers involved in aircraft fires, weve learned that seconds count. Dont delay even five seconds if you detect smoke or fire. Immediately try to extinguish the fire and begin an emergency descent. Even if youre carrying a fire extinguisher and even if you think you have extinguished the fire, get the aircraft on the ground right away.
You cant be certain if the source of ignition has been extinguished or if you have removed a sufficient amount of heat or burnable material to keep the fire from reigniting. The only safe place is on the ground and outside the aircraft.
So again, where to? One thing I like about GPS aids is that you can find the nearest airport at the push of a single button and, with some units, quickly load an approach. If youve had a fire, the best choice for a divert airport is one that has rescue and fire fighting. That usually means at least a Class D or larger airport or, better yet, a major terminal.
In order to have the ARFF unit waiting for your arrival, communicate your intentions with ATC right away and use the word emergency not the phrase a problem.
If you have to shut down the electrical system after that, ATC will have passed along the emergency message and theyll have the equipment waiting for you. Sometimes ATC will ask for other information, including souls on board and the amount of fuel. They would also like to know if theres any hazmat on board. They want to know such information so they can be prepared. But if youre too busy to provide this information, dont worry about it. Get the airplane on the ground first.
What if theres no ARFF airport nearby? Or what if the ARFF airport is five minutes more flying than the closest airport? I dont believe that an extra few minutes in the air is worth the risk of diverting further. In fact, many pilots have performed precautionary off-field landings rather than remain in the air any longer.
Clearly, this is an indication of how bad the fire and heat had become or how badly they wanted to get on the ground. From studying many of those reports, I cant and wont second guess these pilots on what they should have done. The fact that they walked away from a burning aircraft should be considered a good save.
I noticed that several of the aircraft occupants in emergency landings have braced the doors open prior to touchdown, believing this aided their expeditious egress from the aircraft. Your call on that one.
When you do get on the ground, dont forget to shut down the engine and set the brake, if theres time. Its dangerous for ARFF personnel to approach an aircraft whose propeller is still turning or an aircraft thats rolling. And if you can remember, egress and run upwind, away from the smoke and flames.
Given the small number of inflight emergencies requiring a rapid descent, your chances of actually having to do one in the heat of battle are remote. On the other hand, having thought it through ahead of time will keep you from panicking if you ever are faced with the need to get down right now.
Also With This Article
Click here to view “Putting Theory into Practice.”
Click here to view “Critical Factors.”
-by Pat Veillette
Pat Veillette is a safety researcher who works in the training department of a large carrier.