Southwest 1380: think about the flight attendants

Philip Greenspun's Weblog 2018-04-19

The media is gushing over the heroic deeds of an airline captain on Southwest 1380, which suffered an uncontained engine failure. The stories generally do not mention a co-pilot (example) and therefore it would be impressive for this captain to have been the first person to earn a single-pilot type rating for the Boeing 737-700. However, when the airliner checks in with PHL tower, the first officer’s voice in heard on the radio (full audio). Newsweek identifies this pilot as Darren Ellison.

For the pilots of this airplane it was like a normal day in the simulator. Essentially all airliner or bizjet sim training is single-engine operation following a failure because flying a working jet with a three-pilot crew (bulletproof autopilot, left-seat captain, right-seat first officer) is actually easier than a lot of single-pilot operations in light aircraft (hence the higher accident rate for these operations). Thus the “engine failure then land single-engine” is something that a mid-career airline pilot would have done 500 times or more in a sim that is so realistic it can be logged as time in the actual aircraft.

What did happen from the pilots’ point of view? The plane depressurized, necessitating the donning of oxygen masks (the ones in front are “quick-don” types accessible by reaching behind one’s shoulder) and then a reasonably rapid descent from what seems to have been about 32,000′. The goal is to get down to about 10,000′ where everyone can take off their oxygen masks. At the same time, the airplane would yaw because of the asymmetric thrust (dead engine on one side). The plane would have been on autopilot at the time and therefore the yaw damper would automatically kick in some rudder to counteract the yaw.

Usually the crew divides responsibilities between the Pilot Flying, who manipulates the flight controls and/or supervises the autopilot, and the Pilot Monitoring, who does everything else, including talk to Air Traffic Control (ATC). The Captain and First Officer, both of whom are fully trained to fly the aircraft, swap these roles after each leg of a trip. If something goes wrong, the Pilot Flying will take over the radios and thus free the Pilot Monitoring to dig into the checklists, typically accessible via a “Quick Reference Handbook” (“QRH”; see this example from the Canadair Regional Jet (CRJ) that I used to fly). It is the Pilot Flying’s job to ask for the appropriate checklist, e.g., “Give me the Engine Fire Message checklist”. There are some items to do from memory, with the two pilots cooperating so that they can agree on which engine is the dead one and should have its thrust lever cut off, for example.

Airline training stresses the use of the autopilot in an emergency, which frees the human pilots to concentrate on the checklists and not pulling back, for example, the thrust lever on the running engine. The Pilot Flying monitors the autopilot and the Pilot Monitoring is going through the checklists and making sure that items such as gear and flaps are set appropriately at various times.

The Southwest crew was favored with “Day VFR” flying conditions (i.e., it wasn’t dark and there weren’t low clouds over the runway) and were near a super long runway, the 12,000′ 27L runway at KPHL. One any fire is extinguished, e.g., by cutting off the fuel or blowing the squib on a bottle of fire extinguishing stuff (that’s about as technical as we got in training), the situation on a CRJ is no longer considered an “emergency” but merely an “abnormal” operation and the pilots go to the “Single Engine Procedures, In-Flight Engine Shutdown” checklist. The APU is started so that there is a backup source of electrical power (in case the second engine quits!) and various switches are set up so that the dead engine is secured.  Then it is time for “ABNORM 1-9, Single Engine Approach and Landing.” The CRJ checklist calls for landing with partial flaps, thus resulting in a 25 percent increase in landing distance. Full flaps enable landing at a slower speed, but the extra drag means that the remaining engine would be straining to keep the plane on the standard glide path to the runway.

For a plane that ordinarily can land in 5,000′ landing on a 12,000′ runway with one engine is a normal day at the office (sim). As noted above, this is the very situation for which nearly all of airline sim training is directed, albeit usually in uglier scenarios, such as an engine that fails just as the plane is taking off (a “V1 cut”).

If you’re looking for heroes, though, think about the flight attendants. They’re in the back of the plane with 140+ screaming passengers. There is a hole in the airplane. At least one person has suffered injuries that will prove to be fatal. Others are injured as well. They have received no training for this scenario. (Most flight attendant training, as I understand it, is directed at evacuations once the aircraft has landed.)

Some questions that friends have asked:

Why is the term “souls on board” used in aviation? Why does ATC ask? Does it matter if there are 50, 100 or 150 on board? Answer: They want to know fuel on board so they can figure out how much firefighting gear to bring to the scene and also S.O.B. so that they know when to stop searching for bodies. It is the standard phrase even for quotidian matters such as filing an IFR flight plan mid-air (e.g., if the weather turns out not to be clear as hoped).

What is an “extended final”? Answer: Based on the plan discussed in the ATC recording, the plane was lined up with the runway about 20 miles away rather than the usual 7 miles or so (for instrument conditions; it might be only 1 mile at a crazy airport such as LGA in VFR conditions; I wrote about this). That makes life easier for everyone.

Dumping fuel? Answer: 737 does not have a fuel dump capability. If you’re too heavy to land you fly around in circles for a while or just try to land gently so that you don’t stress the gear. If you’ve got a serious emergency and the plane is already damaged it doesn’t matter. You just land overweight. Remember that the max landing weight is for an incompetent landing and is mostly driven by how much abuse the gear can handle.

Do you think damage to cowling/wing/window affected flight performance in any measurable way? And if so, would autopilot recognize and be able to compensate? Answer: The autopilot will manipulate the controls to achieve its programmed goal, e.g., airspeed of 210 knots or heading of 180 (South). Airplanes are usually at least slightly misrigged so that the autopilot will have to hold a bit of left aileron pressure, for example, to keep the airplane from rolling off course. So slight damage to one wing would be like a worse-than-average rigging.

[If you want to truly scare yourself, read Nine Minutes, Twenty Seconds: The Tragedy & Triumph of ASA Flight 529, about Atlantic Southeast Airlines Flight 529, which suffered a prop failure and ended up with a huge amount of drag on one wing that could not be corrected by feathering or any other pilot action. The twin turboprop couldn’t hold altitude on the remaining engine.]

So… let’s hear it for flight attendants who put their lives on the line every day and don’t get to log multi-engine turbine time or look out the front windows. Also for any passengers who got right on a replacement B737 and took off again from PHL to Dallas or wherever else they were ultimately headed. And let’s try to remember poor Jennifer Riordan, the unlucky passenger who died.