In Part 1 (featured at NYCAviation.com), I talked about what happens when stuff on an airliner breaks while we sit at the gate. What do airline pilots do when there is a mechanical malfunction while airborne? Airliners are really complex machines. Just like in your car, sometimes stuff stops working the way it should. Read on to see what we do and how redundant systems keep you safe even when stuff stops working in flight.
The vast majority of flights take place with absolutely nothing going wrong. Modern jet transports are marvelously reliable (even the 30+ year old airplanes). Occasionally, we run into a problem.
Irritating Problems <shrug>
Remember the broken tachometer in your 1977 Ford Pinto? The tachometer is nice to have, but it isn’t a big deal if it doesn’t work. You can drive around safely all day without one.
A similar example in an airplane would be a faulty clock. My aircraft has two of them but we don’t need any to fly safely. If it stops working, we write it in the logbook then resume our discussion of last night’s World Cup match. For the remainder of the flight we’ll use an iPhone as our oven timer.
Small, irritating problems like this happen in airplanes about as often as they happen in your car. A light bulb will burn out or a radio tuning knob will get loose. No big deal.
Check List Problems: Most are not a big deal
As you might guess, we have systems on the aircraft that are a little more important than the clock. For the really important stuff, we have a “Non-Normal Checklist.” When we see a warning light or message on our alert screen, there is a procedure we must follow. The Non-Normal Checklist gives us step-by-step guidance on how to correct or secure the malfunctioning system.
Uh-oh. R HYD PRIM PUMP We just received a warning that our Right Hydraulic Primary Pump has failed. Our hydraulic system powers all the flight controls on the aircraft. Sounds serious, doesn’t it? Surprisingly, the checklist only has two steps:
1. Primary Pump Switch: OFF
2. Continue Normal Flight
That’s it? Yep. My 767 has three separate hydraulic systems. Any single system can bring the jet home safely. There are a total of seven independent hydraulic pumps supplying pressure to the three systems. An eighth pump is powered by a ram air turbine (a windmill) in case we have a really, really bad day. The pumps rarely fail, but if one does, we have plenty of other pumps. After we finish running the short checklist, we put the problem in the logbook. Maintenance will fix the pump at our next destination. Again, we are back to discussing the World Cup until it’s time to descend.
Check List Problems: A few are a BIG deal
Although airliners have plenty of redundancy, there are rare occasions when a problem makes it necessary for the crew to land at an airport other than your destination. This is called a diversion.
My aircraft has three generators to power its electrical system. The chances of any generator failing are very small. But if, by some bad luck, two of our generators stop working, the Non-Normal Checklist will recommend that we find a nearby airport and land as soon as possible. When there is no longer redundancy of a major system (like hydraulics, electrical, or engines), it’s time divert. The cargo customers and/or passengers will, unfortunately, be inconvenienced for safety.
If We Need To Divert To Another Airport…
In this situation, cockpit discussions concerning the World Cup are immediately suspended. There is a lot of work to be done. We need to find an airport that has a runway long enough to accommodate us and good weather to assure a safe landing. Finding a nearby airport that is serviced by our airline is a bonus but not a prerequisite. It’s always nice to get extra help. If time permits, we will contact our dispatcher by radio or satellite phone. Dispatchers can quickly sort through the weather and available facilities at nearby airports and make recommendations. Air traffic controllers will give us preferred routing and keep other aircraft out of our way so we won’t be delayed. While landing, you might see a few firetrucks along side the runway. This is most often just a precaution. It gives the fire and rescue crews some practice and it’s nice to have them standing by in case we need them. Once we are on the ground, maintenance personnel will begin to work on the problem. More importantly, the airline will try to find the fastest way to get a planeload of passengers or cargo to their final destination.
Diversions In The News
The majority of airliner diversions or cancellations are due to bad weather. Weather diversions happen routinely enough that they aren’t newsworthy. An airliner diverting due to a mechanical problem is very rare, so it usually makes the evening news. Don’t let the news reports fool you into thinking that airplanes are unsafe. In my 25+ year airline career, I’ve diverted only twice for mechanical problems. There are about 100,000 scheduled airline flights every day. If the news media reports an aircraft diversion once every 10 days, that represents one serious problem for every million flights. Even a frequent flier is unlikely to experience a mechanical diversion.
Have you been a passenger on a flight that had to divert due to a problem? I’d love to hear about it in the comments below!
On modern aircraft are checklists actual notebooks as pictured or are they electronically stored e.g. iPad? If the former I assume the notebook travels with the aircraft and not the pilot since it would be plane specific. If the latter is there a backup for the electronic device and if so is it another device or a notebook?
Also, when a mechanical in-flight problem occurs is it usually handled by means of knowledge learned from prior training or is the use of a checklist mandatory? Maybe it’s a combination of the two. In a medical emergency “cheat sheets” are generally utilized only after treatment has been initiated.
Thank you for covering another interesting topic.
Great questions. The answers vary depending on the airline. My company uses the spiral bound quick reference book (pictured) for important items we need access to right away. The books stay on the aircraft.
Our iPads contain a lot of other reference documents that we can access.
We have two iPads onboard (plus backup batteries and chargers) for redundancy.
Airlines are experimenting with moving more documents to the iPads.
For your second question: There are a few critical problems that require us to do the first few steps from memory (these memory items are beaten into us during training). After we run the memory items, we grab the checklist and start from the beginning, walking through the whole procedure. Most mechanical problems have a checklist associated with them, sometimes it’s very short, like the hydraulic pump example in the article. When there is a mechanical problem, we always get the book out and follow the guidance.
Both Posts are superb Captain Ken!! Really enjoyed, and learned lots of new things!!
Thank you! It was a fun article to write.
Captain Ken: I can vouch for you that all that goes wrong with an aircraft is duly noted in the
maintenance log book as well as when it is repaired. I worked for UAL for one year in the terminal
maintenance area and the maintenance chief wanted to know what was in each log book to be
repaired and if it was not he wanted to know WHY not. The mechanics did not appreciate me
asking all the time for the WHY. It also drove me nuts trying to please all concerned.
Eventually I left UAL because that field was not very condusive to promotion.
Thank you for articles…
Thank you for the comment. Yep, airlines (and the FAA) are VERY nitpicky when it comes to maintenence and the logs. Making sure the airplanes are perfectly safe is a really big deal.
Thanks for reading!
hi Captain Ken,
i watch aircrash investigation on tv ( lots of them) , i can sense that modern aircrafts are much much safer then for example those from around 80s, or is it because the investigation took decades to be revealed?
interseting topics as always
Aviation has indeed become safer over the past few decades. We have improved safety technology like EGPWS (Enhanced Ground Proximity Warning System) and TCAS (Traffic Collision Avoidance System). Onboard radar has improved, and is still improving. We also know a little more about severe weather, like microbursts, than we did 30 years ago. Along with new equipment, we have better training. Commercial aviation is safer now than it has ever been!
Thanks for reading,
I just recently flew on a plane that was diverted due to icing issues flying from FL to CINCY It was very cold in Cincy. The pilot checked flaps on the wings after backing out, hmmm didn’t sound good. They flew for an hour and turned around and started a descent to land. Slow approach, long runway, took whole runway to slow? Firetrucks/etc. standing by. Very scarey on an airbus 320. Is it possible they knew it wouldn’t work due to cold and were trying to find another plane right away? Diverted in Southern GA. I am just curious. I think our pilot did an excellent job.
It sounds like you had a very interesting flight! I don’t have enough information to guess what the problem might have been.
I can tell you that when there is a problem during a flight, the pilots take it very seriously. When an aircraft diverts to a different airport, the crew is in communication with their dispatchers and maintenance personnel to assure the safest possible outcome.
Often, when there is a mechanical problem with the aircraft (sometimes even minor problems), the flight crew will request that rescue vehicles standby near the runway during landing. Although the they are rarely needed, the rescue personnel add another layer of safety.
Thanks for your comment and thanks for reading!
Had an emergency landing yesterday on United Flight 1064 from Mexico City to Newark. About an hour and a half into flight pilot came on and said please fasten your seat belts and flight attendants please take seats will be doing an emergency landing in 15 minutes into Houston there were issues with the hydraulic system. It was a very short announcement with no details which left all passengers in silence and fear. When we reached the gate there was no check of the plane, we were told automatically that the plane would not continue on and we would be put onto another flight. It was the scariest 15 minutes of my life because we had no idea what was happening. The pilot did do an amazing job getting us past thunderstorms and getting us down gently.
I can certainly understand your fear and frustration due to the lack of information. Sometimes there are situations on an aircraft that put tremendous demands on the flight crew. A hydraulic malfunction often requires the crew to delve into complicated checklists, coordinate an emergency landing with air traffic control, communicate with the airline, and assure adequate emergency services are ready at the new destination. In order to accomplish everything that needs to be done, there often isn’t time to adequately explain the problem to the passengers.
Although it was frustrating, I can assure you that the crew was incredibly busy and using all their training and experience to make sure the aircraft arrived safely.
Thanks for reading!
Got off a ship in Jebel Ali (port of Dubai) and jumped on a Lufthansa 777 to head for home. Stopped in Frankfurt, got underway again and got a hold fire warning lite past Cologne. Dumped fuel and landed in Cologne. Turned out it was spurious. So much vaunted Lufthansa maintenance. Waited hours, got another plane and landed uneventfully at IAD (Dulles). Thank God this incident didn’t happen feet wet.
Don’t be too hard on Lufthansa. Erroneous fire warnings sometimes just happen (fortunately, it’s very, very rare). Glad everything worked out OK for you!
Thanks for reading!
Hello Captain Ken,
I can say yet another great article…. like the way you explain with practical examples and pictures…
I am a System engineer and work for FMS (Flight Management System) development. I wanted to know how critical of FMS failure during flight?
How much pilots are dependent on FMS?
As you have mentioned that It’s challenging to find a diversion airport! I am thinking why not to add a feature in FMS to provide nearby Airport with all the facility available on that Airport (like runway length, runway condition, weather, etc). It can reduce pilot work load in this kind of situation. Your input please…
Thank you for your article ….keep doing good job
We rely heavily on the Flight Management Computers. The 767 that I fly can actually be dispatched without any working FMC, but we have a LOT of restrictions that we must comply with. I honestly don’t think we would actually be dispatched without one, but it’s possible.
As for diversion information, the Honeywell FMC does have an excellent feature. There’s an ALTN (Alternate) page that gives us a list of the closest diversion airports with ETA and fuel burn information. It will even display the ILS frequency for the runway we select. We can quickly obtain more detailed airport information from our Electronic Flight Kit (iPad).
Thanks again for reading!
If there were no diverts, AV geeks in rural airports won’t have a chance to see wonderful planes like 777 ^__^
Well, I can’t argue with that logic!
Thanks for reading!
Was diverted on a 737 from DC to LA because of the bathroom. Supposedly some pump broke, and no toilets could be used 3 hours into the 5 hour flight. Had to land in Denver wait an hour to get fixed, and we were back in the air. Seemed like a bizarre reason to divert, but I guess telling everyone to hold it for two hours was not an option. Got to see a nice view of the mountains on take off from Denver though! Enjoy reading your articles!
That’s a great story. Yep, toilets are really important when you have a large group of people. Besides the inevitable mess and smell, there are health issues to consider as well. Sounds like your crew made the correct decision!
Thanks for reading!
I was flying to a very remote mining exploration site in northern British Columbia. We were packed onto a twin engine Dash along with some mining freight. We started icing up and junks of ice were coming off the props and whacking the side of the aircraft. Some of the miners on board found that somewhat unsettling. Not sure if I was just naive or too dumb but had faith the pilots would get us down safely. Plus there was nothing I could do anyways. We were diverted to an airport in Alaska. Once on the ground were not allowed to get off the plane until some custom guys showed up. After that we could get off but had to stay very close to the aircraft. After a few hours were able to leave and landed on the rather short dirt strip at the camp.
Sounds like fun! When encountering icing conditions, it’s fairly common to have that happen. The props have heating elements in them to help shed ice. As the ice melts, it is flung everywhere, including the side of the fuselage.
Capt’n Ken… Kudos to you and your crew! Outstanding website. January of 2000 I was on a Northwest flight flying from Honolulu to Singapore through Narita. I believe the equipment was an MD11 (3engines). 90 minutes into the flight we heard a loud grinding sound and the plane began lurching back and forth not up and down like turbulance. 30 seconds later the captain is on the intercom explaining we have lost the no. 3 engine, on top. He says we’re getting close to the half way point to Japan; we could make it on 2 engines but he’ll consult the company and give us the decision wether we return back to Honolulu or continue to Narita. I’m sure the captain declared an emergency because we returned back to Honolulu spent the night and continued on to Singapore the next day. Good call by the dispatcher and pilot to return. A lot of work for the company to put a couple hundred people up in a hotel and feed them for the night. Only inconvenience to me was losing my freeday in Singapore before I reported for work.
Great story! It sounds like the crew and dispatchers made the right decision.
I’m getting ready to board JetBlue flight 603 (BOS to PHX) and it has a mechanical issue that prevented us from boarding for about an hour. They just now said it “won’t hold enough fuel” and so they are now stopping in denver on the way to PHX to refuel. Never heard anything like it.
Should I be worried?
You should not worry. The pilots won’t depart unless the aircraft is perfectly safe. Fun Fact: Pilots have families and want to arrive safely, too!