Something to note, is that most commercial aircraft can glide for anything from 20 to 30 minutes from cruising altitude before they reach sea level. I recall reading many news reports of this particular 747 'plunging' to the earth when all engines failed, but that is not the case.
As noted in the article -
> Eventually, after quarter of an hour without any power, the engines were brought back to life.
In fact, every time your pilot/flight attendant announces that you are on descent to your destination airport, the pilots will have pulled the throttle back to flight idle, and your aircraft is essentially gliding down towards the airport. Engines are pretty much not spooled back up until you are on finals, and the undercarriage/flaps etc. are causing a lot of drag necessitating engine power again to maintain approach speed.
An idle 747 has a glide ratio of around 15:1, meaning they can cover ~150km from 35,000ft. My favourite example of this is the Gimli Glider - https://en.wikipedia.org/wiki/Gimli_Glider
Gimli is also my goto example on why metric
should be taught and used in daily life since an educated individual with metric background would likely have caught that calculation error (>1kg/l means a substance with higher density than water).
Engine-off (so-called "dead stick") landings are absolutely possible even in a commercial aircraft, and are something you practise pretty much from day 1 of flight training:
speaking as a former programmer for a large airline, Pilots for small regional jets usually rely solely on experience, while your average cross-country 737 pilot has a co-pilots experience and a small cross-reference manual in the event of failures or warning lamps. you're still "flying" the aircraft with the exception of landing assist and the TCAWS
Jumbo jets are an entirely different beast. You're starting and stopping procedures are similar to any other commercial jet, however large swaths of the plane are entirely computer controlled. this includes jet engine ignition and reignition in case of flameouts. Elevation rate and descent rate are also computer controlled. Pilots in turn are saddled with phonebook sized procedure and countermeasure manuals that determine what to do in the event of anything even remotely out of the ordinary from cracked windshields to broken elevators.
The fact that these pilots could recover from a massive engine shutdown of this nature is remarkable, as most pilots are trained to "never stop flying the plane" in the event of a failure. all engines offline means they either had to engage the APU mid flight to help power auxiliary systems, or they were struggling to manually move hydraulics without any assist. Pilots are trained that engines go through ingestion testing to handle anything and everything, so its not surprising they thought nothing of the ash...A Rolls Royce Trent engine might not seem that large but each one delivers nearly 100,000 pounds of thrust. This, combined with a 10 stage compressor, is enough to overcome even the most furious rainstorms.
> "Good evening ladies and gentlemen. This is your captain speaking. We have a small problem. All four engines have stopped. We are all doing our damnedest to get them going again. I trust you are not in too much distress."
I find something very entertaining when I hear stories of pilots/air traffic controllers communications during emergencies/exciting situations that are extremely calm.
It reminds me of the classic SR-71 Blackbird "Speed Check" story.
Rod Machado, in one of his private pilot manuals, has a story about a Blackbird returning to the US across the Gulf of Mexico and requesting flight level 850 (85,000 ft) from the Houston ATC. The traffic controller, apparently not recognizing the call sign and thinking it was a joke, said something like, "If you can get up there, it's yours." The pilot replied, "Ma'am, we're coming down to 850."
Some friends of mine are, for whatever masochistic reasons, avid viewers of Mayday (aka Air Crash Investigations), and the episode [1] about this event is one of their very favorites.
I recall the episode mentioning that the passengers and crew from this flight have stayed in contact and held occasional reunions ever since.
This show has other names in other countries, and if you can find those edits, is much more enjoyable. Alternatively, you can learn significantly more by just looking up the official NTSB reports that have zero editorializing
Great show, not every episode ends in a disaster. These are interesting stories, learning about the circumstances, watching how people handle these high pressure situations many of us would never have to face and the efforts investigators go to finding the cause/causes of the event. One can also take solace in the fact that although these events are tragic, what we learn from them saves more lives in the future.
I once gave this as a counter-example to the old Alcoholics Anonymous saying "the definition of insanity is doing the same thing over and over and expecting different results."
In this case, the sanest thing to do was to try and try again to restart the engines.
Yeah but just like cars in the desert you risk the dust filter getting totally clogged by the dust. With a car, you can stop and simply unclog the filter by hand - impossible on a piston engine in flight.
Sure, there are at least two ways, but you won't get it fuel-efficient enough for commercial service. You could do research flights into the volcanic ash.
One choice is a low-compression jet engine that doesn't burn hot. Temperatures need to stay lower than the melting point of volcanic ash. Add a durable coating (maybe: sapphire, diamond, tungsten carbide...) to resist abrasion and you're all set.
Another choice is to use an engine that is part turboprop and part rocket. The turbine portion is fed entirely from internal stores, for example liquid oxygen and liquid methane. Keep them balanced for maximum power, or dilute/unbalance them to avoid the need for exotic materials. Ash never enters the turbine. To get back a little efficiency, you put a prop on the front instead of just having a rocket.
You'll want to also put a sapphire coating on the windshield. Treating the wing leading edges could also be a good idea; maybe for that you could consider titanium-aluminum-nitride.
But it still does seem like it could be dealt with - the abrasion does not completely destroy it, so it seems just incremental hardness improvement would handle it.
The damaged blades in the photo are turbine inlet guide vanes. They are attached to the static part of the engine in front fo the rotating turbine and are the first thing the hot (1500C) gasses from combustion hit. To prevent them from melting the blades are hollow and compressor bleed air (300C) flows through them and out the holes visible on the blades. This cooling air forms an insulating layer to protect the blade surfaces. Additionally they will have a ceramic thermal barrier coating. The actual turbine blades are similar except that they have to cope with tremendous loads from centrifugal force and the power transfer from the the gas stream to the shaft.
The damage shown indicates loss of the thermal barrier coating at the leading edge and deformation of the leading edge and the cooling holes. The precise shapes are critical to maintaining the cool air film on the blade. Basically these vanes are toast and in a short time would be burnt melted toast.
Let me recommend the book: “The Jet Engine” published by Rolls-Royce. Jet engines are pretty amazing. They seem simple in principle, but the optimizations needed to make a good one are beyond most countries and companies capabilities.
True, but ablative tips would likely mean engine overhauls at increased frequency, significantly increasing cost. At that cost vs benefit, likely better to just go back to piston and prop.
As noted in the article -
> Eventually, after quarter of an hour without any power, the engines were brought back to life.
In fact, every time your pilot/flight attendant announces that you are on descent to your destination airport, the pilots will have pulled the throttle back to flight idle, and your aircraft is essentially gliding down towards the airport. Engines are pretty much not spooled back up until you are on finals, and the undercarriage/flaps etc. are causing a lot of drag necessitating engine power again to maintain approach speed.