Air Asia QZ8501 is the crashed airplane currently in the news. A popular point in the press is that the pilot requested permission to change altitude due to bad weather. I don’t understand this: the pilot is the person on the scene, so why couldn’t the pilot just instruct ATC that they were changing altitude and let ATC sort it out?
Please, let’s keep this GQ and avoid speculation.
IANAATC
Because ATC are the ones who know what other planes are in the air in the area and what changes in path and altitude are safe to avoid collisions?
Pilots flying under IFR cannot just change altitude or course at their own discretion unless it is for the immediate safety of the flight and they declare an emergency. Pilots are reluctant to do that for lots of reasons and we don’t know that their was any pre-warning for the impending disaster until it was too late to recover from. The flight was experiencing notable turbulence due to being in a powerful thunderstorm but turbulence isn’t considered an emergency by itself. It was also in an area of fairly busy airspace with little to no visibility. Those conditions are one of the times that Air Traffic Control is most needed to keep planes separated and prevent potential mid-air collisions. It would be a chaotic mess if pilots just did whatever they wanted every time they hit turbulence.
At 36,000 ft the airplane is not easy to maneuver. That was probably the reason why he was denied permission to climb that high. Another question is why he did not turn back.
That’s incorrect. ATC initially denied the request because there was heavy traffic at the higher altitude. It’s also rare for airliners to turn back due to weather.
Pure speculation, but this incident reminds me of AF447.
That’s what I read - QZ8501 asked but was denied permission, and because of the storm there were already several other planes flying above the storm cell.
It reminds a lot of people of it and it is probably going to turn out to be a similar series of events that caused the tragedy. As much as the airliner manufacturers don’t like to admit it, it is still possible for an extremely unlikely series of events to get some airliners in an attitude and deep stall that is largely unrecoverable. Thunderstorms are a very powerful force that can trigger a series of events nearly instantly that ensures the inevitable plunge to the surface even without a structural failure of the aircraft itself. Airliners fly through turbulence every day without too much drama but, every once in a while, things line up just right and it results in the inevitable.
The current data suggests that Air Asia QZ8501 came nearly straight down. If you are going slow enough in an airliner and encounter severe wind shear in a thunderstorm (abrupt change in air speed due to changing winds), that can be enough to put the aircraft in a very deep stall that makes the control surfaces ineffective, destroys lift from the wings and makes the aircraft do what gravity wanted it to do all along. It is just an involuntary ride to the bottom for all involved at that point. There may be some other factors like pilot error or instrument failure due to icing as well but even those aren’t strictly necessary if the aerodynamic events line up exactly right just due to freakish but very localized conditions.
So what? The pilot is the one on the scene; ATC are not. If there’s heavy traffic at the required altitude then surely ATC need to get busy?
Thunderstorms in that area go so high that going over the top is not a standard procedure.
Note that besides declaring an emergency the pilot also had the option of clearly explaining that he was in trouble with the bad weather–and ATC would have given resolving this a high priority–but instead it was just a routine change of altitude request.
So it really looks like the plane hit a sudden, bad patch of weather the pilot didn’t see coming.
At the time the risk to the aircraft wasn’t known. Changing altitude without clearance in a busy area is highly risky to your own aircraft and other aircraft in the area. Given the risk of weather vs the risk of collision, chancing the weather is a far better option. The aircraft is designed to handle bad weather it has no survivability when it comes to in air collisions.
Of course in hindsight you can say it was worth the risk because you know the results.
When pilots don’t pay attention to their assigned altitudes, you get things like the Charkhi Dadri crash.
According to this “other incidents” section, they could have put out a mayday call, which is standard procedure when changing altitudes without ATC authorization.
The pilots probably didn’t know if the plane was in extreme danger until it was too late. You are looking at it from hindsight. The Air Traffic Control system is set up for an even more valid reason. It is to keep planes from flying into one another in times of bad visibility (that has happened many times before as well). IFR pilots can deviate from a controller’s orders in times of emergency but only by declaring it as such. However, that course of action also triggers an investigation about why declaring an emergency was necessary in the first place. Most pilots do not want to go through that and understandably so especially if other planes in the area are making it through OK.
The controllers did not do anything wrong. Refusing altitude or course change requests is a routine part of IFR flight to keep all planes in the area safe. That still doesn’t mean that an individual aircraft won’t hit a very unlikely weather related event that causes an unrecoverable scenario.
It has happened in the U.S. before in cases like Delta Flight 191 that got caught in a thundercell on approach to Dallas Fort Worth and crashed due to windshear crushing a passing motorist along the way. One of the least recognized aviation disasters in history happened very shortly after 911. American Airlines Flight 587 out of JFK airport in New York City encountered severe wake turbulence from a leading airliner on November 12, 2001. The copilot overreacted by applying excessive rudder corrections and snapped the tail off. It crashed killing all 260 people on board and 5 people on the ground. Modern airliners are unusually safe machines but they are not perfect. It is very possible for a series of odd events to exceed their design parameters and bring one down with little to no warning.
U.S. airlines are very conservative about flying through thunderstorms especially because we have some of the worst ones on earth but severe ones can happen in lots of places. People complain when they are delayed because of such weather cells but this is the reason why they are always a risk. It is completely possible to end up in a cell that exceeds the aerodynamic design limits of an airliner just through bad luck alone.
A few points.
I don’t know that it’s been confirmed that the pilot requested climb due to the weather. We know he requested deviation from track due to the weather and we know that he requested climb, but I’ve yet to see any hard evidence that the climb request was specifically for the weather. It may have been a routine climb as the aircraft burns fuel, loses weight, and the optimum cruise altitude increases.
Lets say it was for the weather though. It is not normally the done thing to try and out climb a thunderstorm, particularly in the tropics where the atmosphere is thicker, hotter, and wetter, and hence thunderstorms get a lot taller. However there are still valid reasons to climb. You may be flying at a level where you are in clouds, not in thunderstorms themselves, but in cloud between the storms. Thunderstorms like this are referred to as “embedded” and are a pain because you can’t see them, and the best and easiest way to avoid a storm is to visually fly around it. So if you can get clear of the cloud the thunderstorms are embedded in by climbing above it, you can get a good look at the tops of the storms and you have more information to use to pick your way through them.
Whatever the reason for the climb, I’d suggest that the climb probably wasn’t a priority. He’d been given deviations, and that is normally enough to keep the aeroplane safe in the meantime so he was happy to wait for the climb.
If airliners turned back every time they encountered foul weather, there would be thousands more delays than already now.
There was also a case back in the 80’s in the southern USA where an airliner flew into a thunder cell and ingested enough hailstones to kill the engines. IIRC, they almost survived intact, but clipped an light standard while landing on a freeway.
Despite what they say about being protected, I wonder if a strong lightning strike could have knocked out the electrical long enough to cause a severe loss of control?
But yes, the short answer is that the pilot would do what ATC said in controlled space. Technically, the pilot makes the ultimate decision about what to do and can override instructions; but if ATC says don’t climb, the area is already busy, maybe climbing is not a good choice. Perhaps, too, since they could only see the radar for conditions ahead until too late, they did not realize the seriousness of the storm in front of them and did not therefore request urgently enough.
Then you wind up with this radio exchange
ATC: QZ 8501 make a right turn for noise abatement
QZ8501: Noise abatement? I’m at 36,000 feet
ATC: have you ever heard the sound your plane makes when it hits a 747?
Really?
The driver is the person on the scene, so why couldn’t the driver just put on the turn signal (to let everybody know they were coming across all four lanes to get to that exit), and let those other drivers and the Highway Patrol sort it out?
If it doesn’t work on the ground at 65 mph it won’t work in the air at cruising speed. Time is your biggest limiting factor. At those speeds, by the time you see another plane, you’re pretty much dead. Airspace that seems turbulent but safe at one moment can be fatally unsafe the next. Even with all the fancy radar, GPS info, and ATC guidance, there are things that can’t be predicted or avoided. All of those systems are still created by and dependent on fallible human beings.
Take USAir 1016, for example. I’ve been past the crash site often and I’m always reminded of how sometimes, things can come together in just the wrong way.
From the Wiki:
Bolding mine. Instead of whatever happened, Air Asia QZ8501 could have come out of the turbulence into clear skies in the same amount time. Maybe someday there will be planes that have all the readouts you need to avoid every kind of disaster and pilots who can interpret that info at a glance. Today is not that day.
It’s a reasonable question and is more akin to a driver steering across multiple lanes in order to avoid an accident.
There are times when you ignore ATC and do whatever you need to avoid crashing or an unacceptably unsafe situation. Things we practice regularly that include this type of action are wind-shear escape manoeuvres, TCAS alert manoeuvres, and emergency descents. In each of those cases you fly the aeroplane out of the unsafe situation and advise ATC, and/or other traffic, of what you are doing. There are even specific phrases we use to let ATC know that we have taken full responsibility for our flight path.
Lets be clear that it’s not something done as a convenience such as cutting across 4 lanes to make a highway exit, they are emergency procedures to keep your aircraft safe. There are also things you do to mitigate the risk of the manoeuvre. In the case of an emergency change of levels, you can turn off the airway. Any traffic would most likely be directly above or below you so a turn to get off the airway laterally will reduce the chance of a collision. In the case of a TCAS manoeuvre the altitude deviation is normally no more than 500 feet so you shouldn’t come into conflict with other traffic.
Re changing altitude without permission, it’s unlikely to be dangerous. Studies have shown that totally unregulated airspace with planes flying at random altitudes and directions have a far lower chance of collision than aircraft in regulated airspace flying at recognised altitudes and along pre-defined corridors.
There was a famous case not so long ago in South America when two aircraft flying using GPS along a corridor but mistakenly set to the same altitude in opposite directions partially collided. One survived, one went down with the loss of hundreds of lives.
There is reasonably strong support for aircraft to have random offsets from the nominal altitude and track for precisely this reason. i.e. GPS is so good now that collisions are quite likely.
All the Air-Asia pilot had to do was fly to a non integral multiple of thousands of feet - e.g. FL 385 rather than FL 380 or FL 390
See
for lots of math on the subject