Socata TBM Crash in Alberta

[gimmepars]

I'm pretty sure if the same accident would have happened in a King Air or a PC12 (or any other turbine powered aircraft), the 3 degree thing would still have been mentioned in the same way.

To be clear, you think the dividing line between fussing over 3.9° vs 3.0°, and not fussing, is purely because the aircraft was a turboprop?

If a 787 made a 3.9° approach that would be worthy of comment for being too steep. If a 172 did it, you would be laughing at the "space shuttle sized" circuit and too-shallow approach the pilot chose to fly and agree that more circuit practice would be needed.

I'm trying to understand why the TSB thinks the TBM is on the "big airplane" side of that line; it's straight-wing, doesn't weigh very much, approaches slowly. It's also pulled by a prop, not a jet. The report doesn't have much to help me.

Happily I don't work for the TSB, but my reaction to the data would that the pilot lacked proficiency in flying visual circuits and was probably too used to relying on vertical guidance, which he didn't have available. Then he was unfamiliar with the characteristics of the aircraft during a late go-around - again, a lack of proficiency issue, and not one of glideslope. I'm sure the TSB has reached the correct conclusion and that I'm missing something, but I'm not sure what.

They mention in the report that he descended *through* the 3 degree glide path. If you start out on a 3.9, and you end below a 3 degree glidepath, then you are not flying a 3.9 degree glidepath, nor a 3 degree glidepath, and that is cause for concern.

Yes. I'm just questioning the implication that even it had been stable and well flown at 3.9°, it would still not have been "optimal". It was a small plane on a VFR circuit to small non-instrument runway in VMC conditions. That's not addressed in the report.


I get where you're coming from, optimal is a strong word, and it's tough to be right on slope when you turn final in a VMC circuit because there's no visual or instrument slope indications available on the base leg anyway. I didn't key in as much on the deviations from 3 degrees as much though, speed and power settings we're also noted in the narrative and none of those two, or the slope, we're within any kind of stabilized approach criteria, so three out of four variables fluctuating (no mention of centerline that I picked up on)... Time to go flying and come around for another try at it.

[digits_]

Would it make more sense re-reading the report and replacing the 3 degree glideslope factor with an 'unstabilized approach'?

I think one has to read and judge the report as written, and without search-and-replace on the bits that you don't understand!

Paragraph 2.1 does that for you. That's where the stabilized approach and the 3 degrees is tied together. It's also mentioned in the same line with the causes. It's not mentioned as a cause just in itself.

[cdnavater]

The focus on the 3.0 degree final is important because based on what I read this pilot knew or felt he was high based on his actions.
If you are on a 3.0 slope, you will need more power or thrust to maintain your speed and path than 3.9, from what I read he was at nearly flight idle for a good portion and then got low and slow. He then appeared to add enough power to drag it in just short.
My concern was a normal go around was what, 12 degrees, a stall recovery should be quite a bit less to break the stall but this pilot pitched up to 25 degrees, try that sometime, I guarantee 25 degrees pitch at the speed mentioned is well above the critical AOA.
This was a botched approach followed by a really botched bounced landing recovery!

[pelmet]

I am only part way through the report but it looks like the pilot was high, descended through this 3 degree flight path and was then low and then stalled the aircraft. He was probably concerned about the length of the runway.

Bottom line....you have to manage your energy and be aware of it. Being a bit high is no big deal. Descending to be a bit low is no big deal. But you have to manage and remain aware of your airspeed. This is even more critical, when not flying a stable descent.

Ability to fly a steep descent in a turboprop can vary depending on engine type and drag but with a PT-6 with loads of flat pitch(like the TBM), I don't see why it would be a problem. I have flown one complete flight in a TBM700 in the left seat with a ferry pilot into Sept-Iles. I don't remember that much detail about it but it was fairly straight-forward handling, perhaps a bit heavy on the controls, if I remember correctly. I likely followed close to a 3 degree descent but if it was a bit more or less. it would not be difficult.

It is no big deal flying a 3.9 degree descent path in a large turboprop. I used to fly a 5.5 degree glidepath at an airport with a large commercial twin turboprop and it was just a matter of setting power and starting a descent. One had to flare a bit higher but proper airspeed management was key.

This guy got slow and was likely late on adding power. If you are going to dive down through the typical descent path and then reduce the rate of descent for the last few seconds of the approach, you have to be keenly aware of your airspeed and whether you will need to add power(likely if close to final approach speed) or not add power(if you have excess airspeed).

[pelmet]

Finished the report. It appears that it was really just a case of not monitoring the airspeed resulting in a stall.

There is a link to a French report about single engine turboprops rolling over during go-arounds, typically at low speed. I suppose it may be a situation similar to the big WWII fighters with lots of torque. But really, most of have seen what happens in a power on stall.....the aircraft rolls more than with idle power.

Unfortunately, in this large report, the TSB does not discuss the most important thing of all....monitoring your airspeed.