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Posted

 

Another fatal wherein high DA, low perf and downdrafts are seen as suspects.

(It seems that the aircraft was a Comanche not a Cherokee as stated in this video.)

And below is a video made by a local flyer in a bid to better educate visitor aviators about local conditions.

 

 

 

 

 

 

http://www.kathrynsreport.com/2019/10/fatal-accident-occurred-october-20-2019.html

 

 

 

 

 

  • Informative 1
Posted

Have flown 180/250, 260, 260B, 260C models. The 180HP Comanche is a poor performer in higher DA, eg, >5000. Hard to accurately lean a carby engine for best power take-off. FI better, but need a multi point EGT as well. 

No info as to configuration for take-off, nor the technique used to rotate and if it was held in ground effect to gain IAS. All very important. Wonder if pilot had any form of training, or any briefing on high altitude ops?

 

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  • Informative 1
Posted

Were the wheels retracted?. These planes have a simple flap that doesn't provide good extra lift for the extra drag involved. I calculate the DA to be under 9,000 feet. The  "service" ceiling is where you still make 500 FPM and I would have thought  would be around 12000 feet at least. The wings are of the Laminar flow type where they stall more sharply than others and you need to have the right speed and not be slow. Turbulence degrades performance also. Nev

Posted

At these high DA the mixture must be leaned to get the peak RPM. Because the MP is very much lower - take off 1" for each 1000 alt, the aircraft can be held on brakes then carefully leaned. In this case it would probably have only made 21-22 " MP, (60% power?).

 

FWIW, I would have leaned it, then used every metre of runway in a 'rolling' take-off,but zero flap. Then, rotated by  clicking in flaps 1 via the reliably positive manual flap bar - but holding in ground effect while retracting. 

 

There are undoubtedly other factors involved, eg engine condition, but 180HP...........  you are always going to struggle.

 

Having a substantial downhill slope,(5-15%), was our saviour in PNG, where OPS at 7-10,000 DA were common.

  • Like 1
Posted (edited)
9 hours ago, poteroo said:

At these high DA the mixture must be leaned to get the peak RPM. Because the MP is very much lower - take off 1" for each 1000 alt, the aircraft can be held on brakes then carefully leaned. In this case it would probably have only made 21-22 " MP, (60% power?).

 

FWIW, I would have leaned it, then used every metre of runway in a 'rolling' take-off,but zero flap. Then, rotated by  clicking in flaps 1 via the reliably positive manual flap bar - but holding in ground effect while retracting. 

 

There are undoubtedly other factors involved, eg engine condition, but 180HP...........  you are always going to struggle.

 

Having a substantial downhill slope,(5-15%), was our saviour in PNG, where OPS at 7-10,000 DA were common.

It is easy to lean for maximum rpm and therefore power with a fixed pitch propeller. With a constant speed hydraulic control propeller how would the pilot know when it is producing maximum power? I don't think I was ever taught this.

Edited by Thruster88

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