FlightAware Just looking at a flight from August, shows aircraft filed for 410 and 10 minutes into the flight was at flight level 240 - fsmex poster state aircraft was at flight level 270 when it 'fell' from the sky to 8300 feet in seconds and was off the radar in less than 14 seconds. (unconfirmed)
Rapid D from FL270 is not that dramatic if you have working O2 masks from an inadvertant demo done by a B-727 FE while I was deadheading in the back years ago. We were over Florida, got the fog in the cabin and started the emergency descent. After a long couple of minutes, pressurization was restored and we pressed on to a landing, we were near top of descent when the incident occured. Of course, at 0330 with a tired crew in mountainous terrain, the outcome might not have been as favorable.
Any report of a classic Lear involved in a possible upset at altitude brings back memories of the infamous 'go fast' switch that was installed illegally in many planes.
Here's a remembrance from an AVweb columnist:
I was luckier than some of my contemporaries who went to work for companies that had either no scruples whatsoever, or no understanding of high speed aerodynamics combined with high altitude meteorology. Those operators were the ones who put "go fast switches" under the panel of their Learjets. The switch disabled both the overspeed warning and stick puller. The 20-series Learjets have so much power they can exceed redline airspeed in cruise flight. Doing so is an exceedingly serious affair because at some speed past redline it induces what is known as "Mach tuck". When that happens the airplane begins to pitch down, eventually uncontrollably until the airplane violently comes apart. There is a very limited time for a well trained crew to take precisely the correct action to save the airplane and themselves. While I was flying as copilot there were some inflight breakups of Learjets, notably freighters. It was later discovered that go fast switches were to blame in at least some of those tragedies.
The Pilot's Lounge #134: Gear Up, Good Night — Flying Freight in the Not-So-Good Old Days
If the plane really did fall out of the sky at FL270 that would still be below the region where Vmo (306 kts) would catch up with Mmo (.82). It is alleged that the Lear 23 originally had a Vmo of 350 knots but when the Model 24 was produced it was over 12,500 lbs. and became a FAR 25 aircraft. Among other things, this meant that the windshield had to be tested with the unlucky four pound chicken shot out of a compressed air cannon.
Apparently 306 knots was the fastest chicken that didn't break the windshield so that became certificated Vmo. Back in the cowboy days of Lear flying on some Lears the 'go fast' switch would raise the barber pole back to 350 knots since in the U.S. (and Mexico for that matter) you would be 250 or below until you climbed above 10000 and there weren't many four pound chickens above that altitude.
At least some Lear mishaps were thought to be caused by a redline 350 knot climb causing an inadvertant mach overspeed at some point and resultant loss of control.
350 knots at FL270 on a standard day is about mach .86 I calculate.
Hopefully the Lear 'go fast' switch is just a bad memory but it raises a possible classic Lear mishap scenario. I still have colleagues who absolutely love to climb a jet at barber pole speed, even with hills around.
Another report about reaching FL 350, followed by a very rapid descent:
I wonder if they really made it to FL350 in 62 miles or if that was the filed altitude? As in the AA Cali crash, the translation sometimes helps propagate reporting errors among journalists not familiar with aviation.