Originally published at: Laredo Accident: When a Vibration Becomes a Warning
Preliminary findings from the Laredo Citation crash offer pilots a sobering lesson in recognizing unfamiliar anomalies, resisting bias, and declaring emergencies early.
As a former NJA pilot with loads of experience in the Citation Latitude, as well as an experienced accident investigator from the US Navy and a graduate of the Naval Aviation Safety School, I would argue against jumping to the conclusion the pilots were at partial fault for not heeding an unknown vibration / noise. It is true that these things are possible signs of a serious problem, but once in flight over Mexico, I cannot say that a declaration of an emergency and a landing at just about any airport in Mexico would have been the proper course of action.
The aircraft system’s EICAS should have provided more timely awareness of the impending failures, as well as true separation of critical systems (I.e fuel and electrical.). Cessna / Textron has a long history of cobbling together systems from older approved designs (The Latitude shares many commonalities with the CE-680 Sovereign) that may not reflect a robust Part 25 design, although so approved. Often NJA will discover issues that no one else finds because the aircraft is operated 4-5 times more per year than a typical Part 91 firm.
I would submit this tragedy could not have been prevented due to multiple design failures couple with a lack of thought put into the EICAS to alert the pilots of a major failure. Relying on ‘gut’ instincts and vibrations, sounds is a good technique for GA pilots flying 50 year old piston aircraft, but shouldn’t have any place in flying a modern jet equipped with the latested systems.
My friend, a former Jaguar pilot with the Royal Air Force of Oman, was on a long-range mission with two large drop tanks. At the stage where he was at the point of no return he got a fire warning from the reheat zone. Some quick thinking deduced that he was in a sticky position. If he ditched the tanks he would definitely not have enough fuel to get back, but if he kept them his fuel consumption would mean he would be VERY tight on fuel. He kept the tanks and sneaked it in with no diversion fuel..
The cause was a thrown turbine blade, which set up vibrations that happened to be at the resonant frequency of the reheat fuel delivery pipe, which promptly fractured causing the fire.
This accident could well be caused by sympathetic vibrations!
Teresa I thoroughly enjoyed reading your write up of this incident. Helped me understand a lot of stuff in your step-by-step, slow progression and explanations really helped my knowledge grow so appreciate the clear concise article.
Thank you
There are serious flaws in your analysis:
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Reportedly the pilots also talked to a maintenance person. That is far more than just talking to flight ops.
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The ultimate/higher authority is always the pilot in command…not ATC or flight ops.
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The plane likely crashed due to fuel starvation yet the preliminary report and your analysis do not discuss that. If the two fuel tanks are normally isolated, how did a “rupture” in the fuel system on the right side cause a complete loss of fuel?
As for the right 270 degree turn that put them on a long final, the pilots probably made a fatal mistake with that. State “unable” and descend over the Laredo airport.
I am not that concerned about the original problem. They sought input. There was probably no way to know that a generator was about to grenade itself or that a fuel system tube would fracture.
What concerns me is that there is zero talk of what likely caused the crash…running out of fuel and secondly not descending over the airport.
I am not any kind of heavy metal flyer, but l do know and understand that a vibration that arrives via the shell of the aircraft is a whole ball of wax and a few orders of magnitude difference in energy level than a fan in the avionics. A simple walk of the plane should have told them all they needed to know.
Also, I did a 737 SIM weekend with United just before 9/11. Preparation for that was an extensive review of the aircraft systems with a particular emphasis on what could go wrong and what signature alert profiles they would throw.
If that level of detail is no longer expected of pilots, then this type of thing will happen more and more often. PIC means exactly that.
I’m not commenting on this crew in particular, but knowledge of your aircraft systems to the greatest extent possible is a must. The author states “one can also not assume that the crew understood the aircraft’s design ‘well enough’ to know that the engine shaft cranks an accessory gearbox to allow the generator to supply electrical power”. While that may be a plausible observation, it bothers me. Again, not commenting on what this crew did or did not understand, but if you are flying this level of airplane and you don’t understand something like what accessories come off the engine and how they are powered, then you should not be flying that plane, nor should you be able to pass any credible ground school or checkride. Systems knowledge will at least give you a chance to connect the dots from what you see and feel, back to a potential root of the problem. Please note that I said “a”, not “the”, because you may not know for sure; be open to modifying your analysis. It does help to have a good EICAS design on your side, but it isn’t a substitute for raw knowledge. I flew a plane for years where ‘root’ messages, i.e. pertaining to the component related to the primary problem, were displayed at the top of the stack, with consequential messages following. Either way, give yourself a chance to deduce the potential ‘root’ cause of problems by spending time in the AOM when not flying. Flight display / ADC reversion to backup configuration, okay. Accompanied by electrical system abnormalities, okay, maybe not just a screen or ADC component failure. Accompanied by vibration, okay now something mechanical is happening, the generator?..Do we see engine core vibration? No? Okay, maybe isolated to the engine accessory section. How’s my fuel? Look at the tank totals. Wow, fuel imbalance is developing. Potential fuel leak. Okay, declare an emergency, get the airplane on the ground. Do I have enough fuel with a potential leak? I know my AOM fuel imbalance limit in pounds is X. How will the imbalance affect the way the airplane handles? Does it make sense to crossfeed, or will that just waste fuel we can’t spare? Single engine options. Copilot flies and talks to ATC after a plan is agreed upon. Captain handles checklists, briefs passengers, and advises ‘company’ if time allows. Captain probably takes flying duties back for approach and landing. Study your AOM. Then go through scenarios like this in your mind, at home or in the hotel to give yourself a fighting chance to enjoying a long career.
I must be a little lucky. I’ve had a blower motor go up in smoke, 5 miles from an airport. Put it down, and called the owner of the aircraft to pick me up. Microphone switch break, close to another airport. Circled just outside their airspace, and they vector me in. Lost an alternator on a return trip, 5 miles back to home. Tachometer cable snapped just outside the quad cities approach control. Luckily there wasn’t an engine issue, and again, i made it back.
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