You would think crew may have chose poorly. But old saying goes... "Tuition comes at a high price."


https://aviation-safety.net/wikibase/349825

 

That is not a 12 knot tailwind.

 

Closer to 8 kts on the tail. Not ideal for a jet on a 5700' runway, but should have been safe enough if it was dry, and they had good numbers.

The automated weather doesn't tell you anything about rwy surface conditions though.

 

If the assignment was to fly to Livingston, there are six runway choices: runway 22, which they used; 4; 8; 26; 13; and 31.

Runways 8-26, and 13-31 are both turf, and 4,600' long. Neither appropriate for the Lear 55.

With reported wind 090 at 12, runway 22 had a 7.55 knot tailwind, and a 9.33 knot crosswind.

With the same wind, runway 4 had a 7.55 knot headwind, and a 9.33 knot crosswind.

Both runways had the same crosswind component, albeit one left, one right. As Rickair7777 noted, runway 22 offered approximately 8 knots tailwind, vs. the opposite-direction runway 4, with the same value headwind.

What is not indicated, as Rickair7777 noted, is runway condition, but also unknown is the landing technique, or approach speed. It's very possible that the runway choice had little to do with the overrun. Slightly higher energy and groundspeed, but if they flew the approach fast or landed long, then the tailwind was nothing more than window dressing.

Everybody who hasn't landed with a tailwind, stand on your head. Look, no one is standing on their head.

Everyone who knows where on the runway this crew landed, or what they used for an approach speed, or their landing weight, or the runway condition, raise your hand. No one is raising their hand.

The mishap occured at nine in the morning, with snow on the ground, which is visible in picutres of the mishap aircraft, intact, in a ravine off the end of the runway. Not evident is whether snow, ice, or frost was on the runway

With 1900 overcast, an approach was in order, at least to get below the overcast, and Flightaware groundtrack appears to suggest the crew flew the RNAV (GPS) 22. It has an 8.6 degree offset. The descent path and. VGSI angles are not coincident. Circling minimums are provided, but circling to runway 4 is on the terrain side, with the closest terrain at 9,300' and a MSA of 12,600. Additional remarks for the airport list for runway 31 a mountain at one mile, 23:1 ratio.

Circling is not authorized for runways 8-26, or 13-31. Circling not authorized southeast of 4-22. Big hills.

Livingston is a mountain airport, subject to mountain winds, which are seldom steady, and above ground level, the crew may well have experienced turbulence due to the mountains (normal in that area), and had reason to believe that the winds at the surface might not be any smoother. Yellowstone Air Service's slogan at Livingston is "Skip the wait in Bozeman! Visit Livingston, where the wind blows, but the service doesn't!" Additionally, Livingston is a cold weather airport, requiring cold weather corrections (required below -29C). It was cold. While temp corrections might only be required below -29C, they may be well advised at warmer values, too. We don't have information as to whether the crew applied any corrections, or not, or how that may have affected their approach or altitudes along the approach, or arrival altitude at MDA, when they began descent from MDA, or again, even their speed at the runway or technique. Did they hold it off? We don't know.

It's hard to crucify someone based on incorrect information when so little is known, isn't it?

 

Did some sleuthing in my Phenom 300 light jet performance app. Runway required goes up by approx. 3% (2.8-3.4% at light/max landing weight - S.L, 5000', 10,000' airports). So 5,701' at 4,659' makes the 5,701' runway more like a 4,914' at S.L.

At KLVM an 8 kt tailwind vs an 8 kt headwind the required runway length at max landing weight increases by 883'. At a light weight the difference between an 8 kt tailwind vs headwind is 751'.

The Lear uses more runway than the Phenom 300 based on the approach speed data I found. Minimum approach speed is 12 (???) kts faster. Not a perfect analysis but adding a 10 kt tailwind (ie the LR55's higher approach speed) increases the 1.67 landing distance by 720'.

Take the elevation adjusted airport equivalence of 4,914', subtract 720' (?) for the faster approach speed (if anyone has actually LR55 landing performance it would be more accurate), and take away another 883' for a tailwind and might be similar to landing a Phenom 300 on a 3,311' runway??? The 'sketchist' we go into, that I know of, is 4,451'.

They certainly didn't put all the factors in their favor. (headwind vs tailwind).

Per the news article the FBO personnel said the plane went off the runway by about 500'.

 

Just sayin’

 

Reported weather: [/size]KLVM 111553Z AUTO 09012KT 10SM OVC019 M17/M19 A2968 RMK AO2 SLP131 T11671194

Field elevation: 4,659'

Pressure altitude: 4,883'

Density altitude: 2,115'

 

We have to wait for the NTSB to issue a statement with a Visual model of the accident, Aproach Profile, IAS vs GS,, and touchdown point on the RWY.

 

Good catch. But it's still 7.5% (?) less (using my a/c's performance) vs a standard day (15C) of a 5701' at S.L. The equvialent distance would be 5,268'. The tail wind vs headwind impact would still be there (albeit perhaps slightly different at 2,115' D.A vs 4,6xx').

 

I don't have Lear 55 data with me and I'm too lazy to go in the other room and pull up Lear 35 data or charts; the Lear 55 uses Lear 35 gear and brakes, and weights about 3,000 more at gross weight. Otherwise very similar speeds and performance, though the 55 goes higher.

The 55 operators advise 2,800' landing distance, without specific qualification.

Personally, having flown in and out of Livingston and Bozeman, I'd have preferred Bozeman, which isn't far away. 1.67 landing distance becomes an issue for dispatch purposes, but not for operational purposes; one doesn't need to see that value before starting an approach. For dispatch purposes, under Part 135, the airplane must be able to land in 60% of the available dry runway, or specifically, 1.67 times the landing distance of the airplane must be equal to, or less than the available runway landing distance. For dispatch purposes, the airplane landing distance data would have needed to show that the airplane coiuld land and be stopped (after passing a threshol 50' obstacle) by 3,420;. If 1.67 times the manufacturer performance data showed a landing distance of that value or less under forecast conditions, then the airplane was legal, on a dry runway.

No doubt that information, or some approximation thereof, will be available with the accident report.