Breaking News Lear Jet crashed

[Mr Pink]

All of the above.

We also need to discuss just how narrow the safe flight envelope is for a modern swept wing corporate jet at cruising altitude. The difference between overspeeding the aircraft and stalling the aircraft can sometimes be as little as fifteen or twenty knots of airspeed.

Icing on either the wings or the horizontal stabs can initially cause the aircraft to begin nosing over. In a Lear jet like this, an effect known as Mach tuck can start to appear very rapidly, further worsening the situation.

As for the girl pilot, I’m less inclined to question her chromosomal makeup, than I am to question her age and experience. Quite often, the hardest part of being an F.O. is having the confidence and the cojones to question a bad decision that is being made by the captain. And that reality holds true independent of one’s sex.

I’ll be curious to see what we might learn about the capabilities of the weather radar on that particular aircraft. Those cells can build quickly, particularly in South Florida. But this one seemed to have been established long enough for it to be avoided.

Just by coincidence, I asked that question to my captain the other day. The wide body we were in had a safe range of about 40 knots. Below that and you stall, above and you over speed.

It sounded pretty narrow to me but he said it wasn't too bad. But is might start to sound smaller and smaller when you are dealing with irregularities.

I've heard mach tuck mentioned here and there. If I remember from my ground school, it's an effect of over speed where too much of the airflow across the aircraft is supersonic or above, then the nose drops out. I can't see that happening to induce the dive, and I don't know how much effect it would have after you were already going almost straight down. So doesn't seem like it would fit into the puzzle.

Problem is, we won't know how fast the plane thought it was going (IAS) in order to determine over speed or stall (at level flight before the dive). Simply how fast wind is flowing over the wings is all the plane knows. Takes into account winds aloft and wind direction. Air temperature and density have a major impact on lift too. The ADSB data everyone is pulling from shows ground speed i believe. Doesn't sound like there was a data recorder so we may never know the exact parameters at altitude
IAS is why you could hover in a cessna if you put a giant 60-70 mph fan in front of it. Doesn't care about the ground, just airflow. That airflow is indicated air speed IAS

Also, weather radar can be aimed up and down. If you don't have it pointing at the weather, you don't see any weather (FO job). It seems they were flying above the red blotch...but that is still not a good place to be in when you have massive thermal updrafts with precip, ice, hail and/or supercooled droplets.

Regs say you are to give those kinds of storms a 20 mile avoidance... LATERALLY, not right on top of it.

I'm gonna call poor pre flight planning, possibly inadequate briefing for irregular operations, poor route planning through dangerous weather with apparently no contingent plans. Failing to use ATC for a second set of eyes, possible poor CRM...but that isn't really known, and it is more a thing of the past now. Although, with that lopsided of a crew dynamic, I can believe it could creep in unintentionally

 

[Head Censor]

Just by coincidence, I asked that question to my captain the other day. The wide body we were in had a safe range of about 40 knots. Below that and you stall, above and you over speed.

It sounded pretty narrow to me but he said it wasn't too bad. But is might start to sound smaller and smaller when you are dealing with irregularities.

I've heard mach tuck mentioned here and there. If I remember from my ground school, it's an effect of over speed where too much of the airflow across the aircraft is supersonic or above, then the nose drops out. I can't see that happening to induce the dive, and I don't know how much effect it would have after you were already going almost straight down. So doesn't seem like it would fit into the puzzle.

Problem is, we won't know how fast the plane thought it was going (IAS) in order to determine over speed or stall (at level flight before the dive). Simply how fast wind is flowing over the wings is all the plane knows. Takes into account winds aloft and wind direction. Air temperature and density have a major impact on lift too. The ADSB data everyone is pulling from shows ground speed i believe. Doesn't sound like there was a data recorder so we may never know the exact parameters at altitude
IAS is why you could hover in a cessna if you put a giant 60-70 mph fan in front of it. Doesn't care about the ground, just airflow. That airflow is indicated air speed IAS

Also, weather radar can be aimed up and down. If you don't have it pointing at the weather, you don't see any weather (FO job). It seems they were flying above the red blotch...but that is still not a good place to be in when you have massive thermal updrafts with precip, ice, hail and/or supercooled droplets.

Regs say you are to give those kinds of storms a 20 mile avoidance... LATERALLY, not right on top of it.

I'm gonna call poor pre flight planning, possibly inadequate briefing for irregular operations, poor route planning through dangerous weather with apparently no contingent plans. Failing to use ATC for a second set of eyes, possible poor CRM...but that isn't really known, and it is more a thing of the past now. Although, with that lopsided of a crew dynamic, I can believe it could creep in unintentionally

All excellent points.

Mach tuck may or may not have played a role, but as I understand it in the Lear 60, it can begin to present itself very quickly after the over speed regime has just barely been entered. I imagine in this scenario it would have been more of a contributing factor rather than a causal factor in the aircraft beginning its rapid descent. I can see a scenario where they found themselves experiencing light, manageable frost type icing right up until they actually entered the core of the cell, at which point the icing intensified more rapidly. If the icing effect was felt more on the horizontal stabs, that loss of downforce could have easily began dropping the nose.

Whatever it was, it surely happened quickly. Based on the data I’m seeing, they went from a gentle, commanded 700 fpm climb, to a descent rapidly passing through 10,000 fpm in less than 13 seconds. Another 10 seconds after that, the descent rate was well over 20,000 fpm and accelerating.

 

[Mr Pink]

All excellent points.

Mach tuck may or may not have played a role, but as I understand it in the Lear 60, it can begin to present itself very quickly after the over speed regime has just barely been entered. I imagine in this scenario it would have been more of a contributing factor rather than a causal factor in the aircraft beginning its rapid descent. I can see a scenario where they found themselves experiencing light, manageable frost type icing right up until they actually entered the core of the cell, at which point the icing intensified more rapidly. If the icing effect was felt more on the horizontal stabs, that loss of downforce could have easily began dropping the nose.

Whatever it was, it surely happened quickly. Based on the data I’m seeing, they went from a gentle, commanded 700 fpm climb, to a descent rapidly passing through 10,000 fpm in less than 13 seconds. Another 10 seconds after that, the descent rate was well over 20,000 fpm and accelerating.

I was speaking to the initial nose down/roll action in specific. For mach tuck, you have to overspeed near or past mach 1 to develop it. I don't know how that plane could have done that when heavy with ice. Plus, they were climbing a bit.

It is nitpicking, I know. I just happened to always find the subject of mach tuck interesting. Mach tuck is one reason that only v-shaped wings can go past mach 1

Swept wings, like on most planes, actually have some airflow over the top of the wing that hits mach speed because it is going a longer distance over the top curve in the same amount of time as the other airflow, but the overall airspeed of even the fastest planes is around .92 mach (92% of the speed of sound). And that number changes with air temp and density so there is no exact speed for mach 1. You probably knew all that, just interesting tidbits for those who don't know.

 

[Head Censor]

For mach tuck, you have to overspeed near or past mach 1 to develop it. I don't know how that plane could have done that when heavy with ice.

Thanks for the engaging back and forth, Mr Pink.

My knowledge of this subject may be slipping with time, so apologies up front if I have this wrong, but it’s my recollection that the Mach tuck phenomenon is specifically tied to the critical Mach number (Mcrit) of the wing rather than the aircraft’s actual speed through the air. As such, it would be possible for Mach tuck to become a controllability issue at a point significantly before the entire airframe has entered into the trans-sonic regime. Subtle changes to wing shape brought on by icing could cause this phenomenon to appear at an even lower actual airspeed for the reasons you’ve so eloquently already described.

Either way, what we now know for sure is that the situation went from seemingly controlled to unsurvivable in the span of about 13 seconds. Mother Nature can be brutally unforgiving at times.

 

[xavier]

So according to NTSB the elevator has been confirmed to have fallen off the jet at some point ... since pieces of it have been found away from the crash..

Without that elevator the airplane would have been unflyable and more than likely would have nose dived

Also my understanding is based on where they find the majority of the elevator will likely determine what the cause was

if the majority of the elevator is found miles away then more than likely there was a major mechanical malfunction that caused the elevator on the vertical stabilizer to fall off

If the pieces are found closer to the crash then more than likely it was icing that caused the plane to nose crash and the 30,000 ft per minute descent ripped that rear elevator off the airplane

 

[DbD]

Elevator going down.

 

[Mr Pink]

This is about the best roundup I've found from a pilot and he addressed most of the things were were talking about above.

He discusses the ability of convective storms to launch moisture upward at an astonishing volume and velocity. Also the weather radar tilt function, and if it's pointing in the wrong direction, you can completely miss what you need to see.

Some have wondered why she had to tell the captain to 'look at the ground' (as if he wasn't paying attention or had given up), but I would argue that if the just broke below the cloud layer, he was still buried in the instruments and not yet transitioned to visual flight.