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Two fatal crashes in France today F-GIKZ and F-GSBS

Antonio wrote:

Now I fly a turbocharged aircraft which is less affected, but nonetheless have endured two high-temperature related situations:

The required GS/TAS on wheel to match the liftoff IAS at VS will be a problem for all aircraft (and cars) but that is about 20% at FL100 (maybe more with temps corrections), although it has a ^3 factor in ground roll, so more a +60% runway length in turbo engines

But the elephant in the room is engine power at FL80 your max on NA is 70% will may make +160% runway length
Something like Groud_Roll% = (Power_SL/Power_Altitude)*(GS_Altitude(ASI=VS))^3

If one is planning to go above MTOW by accident or on purpose, the physics suggest they should also adjust ground roll for increased VS with some G-factor and climb for decreased VY as the polar curve shift back, at +30% above MTOW most SEP with “quadratic polar curve” simply can’t fly and if they magically fly they still can’t maintain a turn without going down, as first proxy the spread VY-VS is their friend as well as power required to maintain high G-loads turns

Antonio wrote:

Interestingly this computer also provides expect ROC at Vy for NA aircraft. If you get a zero, it does not matter how long your runway is : you will not make it.

KOCH chart is my friend, it is generic to all aircrafts but assumes NA engine and 16kft ceiling (as well as linear profile for ROC & acceleration)

Last Edited by Ibra at 15 Sep 10:54
Paris/Essex, France/UK, United Kingdom

I love that the take off calculator includes gross weight at 120% of maximum

I might have to get one of those!

Sans aircraft at the moment :-(, United Kingdom

Ibra wrote:

Archacon is sea-level and 1.5km long, would you takeoff 4pob in 120CV Robin at MTOW in hot day? I see no reason why not? would I do it at 6000ft DA, absolutely NO even if it’s “ok for POH”

Agree that at Mtow, it should be a 590m long takeoff with a 500ish ft/s climb, with potential margin for safety.
For the Arcachon crash, I would think of a loss of control or an EFATO indeed. The fact is, at Mtow, you cannot stay close to stall speed, you need a margin because it takes more altitude to recover. Another circonstance is that Landes is full of trees, and in case of an engine failure, the green see welcomes you.
I got this Koch Chart for mountain rating ;).

Last Edited by greg_mp at 15 Sep 11:13
LFMD, France

Ibra wrote:

KOCH chart is my friend

Seems the same as the TOPC for given conditions. The good thing of “my” TOPC is it that additional to temp and pressure altitude, it also factors surface type, gradient, wind and TOW, and that it works for turbocharged pistons too!

Either the POH itself or even better it plus a supplement with one of these “computers” (I can envision youngsters wondering why we call that thingy a “computer”) and previous experience in non-critical situations are must-haves for DA-limited take-offs. Otherwise you do not know how big a safety margin you are using.

Antonio
LESB, Spain

it does not matter how long your runway is : you will not make it.

Are there many such planes?

I mean for “normal” runway elevations and temps e.g. no more than 4000ft and +30C (LESA might be one close to that, on a bad day, but it is a long runway).

Administrator
Shoreham EGKA, United Kingdom

Well if your airfield is at 2000ft altitude on a low-pressure day, say 990mbar, at 40C, you’ll be losing 60% of your climb performance in optimal conditions.
If you only had 500fpm to start with, the result is 200fpm, which is not much of a climb, and any small over- or under-speed vs Vy or error in calculation or 10 deg bank and you get a resulting zero ROC. Then try to reduce power after take-off …

Antonio
LESB, Spain

Peter wrote:

Are there many such planes?

NA Arrow 180 at 4000ft will never accelerate or go up to any meaningful climb speeds with it’s gear down, so you may have to pull it up in ground effect, this trick may not please those who wait for positive rate of climb or remaining runway to finish before putting Gear UP

greg_mp wrote:

Another circonstance is that Landes is full of trees, and in case of an engine failure, the green see welcomes you.
I got this Koch Chart for mountain rating ;).

Yes sadly, the trees is the only option around there

Is there a Koch Chart for Mountain Rating on twins ?

I got checked on site where they gave that chart, for Jodels/Cubs a factor of 300% will never spoil the party !
A 300ft ground roll at sea level is 300m at +8kft altitude, should work when the runway is 900x something

Last Edited by Ibra at 15 Sep 12:39
Paris/Essex, France/UK, United Kingdom

The crash site near Arcachon is 2km from the runway, and the pilot has apparently reported a flight control issue on radio (it is an AFIS field).
The pilot was found out of the aircraft, which was on fire when rescue came. The poor passengers were still in the cockpit.

According to a picture here , the Robin that crashed in the Alps hit the mountain, apparently below the pass.

LFOU, France

Jujupilote wrote:

a flight control issue

I am not familiar with the type, but could the typical loss of lateral control associated to slow flight be mistaken for a flight control issue?

Antonio
LESB, Spain

FYI There is another DR400 that has gone down (FGMRV at Prades) but everyone was OK…
(Local paper has photo with Reg, repeat all OK this instance)

Can confirm (Im ’tother side de la Bassin) that Saturday afternoon was REALLY hot… definitely 30+degC.
I spent the morning at our aeroclub helping host a small ULM gathering and after lunch I escaped home to the pool…

Regards, SD..

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