Although I have a few hundred hours in C404 and a few tens in C421, I abhor the Cessna fuel systems.
Most of my thousands of MEP hours are in PA23 and PA31, and they both have the simplest of fuel systems, and the PA34 is even simpler. Why is it that Piper could create really simple systems that just, er, feed fuel from any tank to any engine at any time with the minimum of switches, and Cessna had to have these Byzantine systems?
My C310 had that devilish fuel boost set up. It was supposed only to be set to the “armed” setting on full power takeoff and initial climb. There was also a mod or SB that took the pressure switches out of the system, with a checklist change to manually switching to hi in the event of a power failure on takeoff. Crossfeed would only be selected in cruise flight, with the pumps on the low setting or off. But murphy’s law…
Recently, it is quite common that accidents happen to be recorded due to widespread use of smartphones, security cameras etc. This is the case with the C421 accident we are talking about here. The footage showing last few seconds of ill fated OK-TKF were published by one of the Czech TV chanels. It shows the aircraft falling down helplessly in a flat spin and the fireball caused by huge quantity of fuel onboard.
The recording can be seen here:OK-TKF accident
Pytlak wrote:
It shows the aircraft falling down helplessly in a flat spin …
It’s really difficult to see in this video but to me it looks like an inverted spin. This would also explain why the engines were not running.
That’s a flat spin. Wonder how he got himself into that?
what_next wrote:
It’s really difficult to see in this video but to me it looks like an inverted spin. This would also explain why the engines were not running.
I watched it on a large screen, the aircraft is level and upright, it is a flat spin.
An outcome for normally aspirated twins if the pilot allows allows speed to reduce close to stall asymmetric – Vmc being below the stall at altitude for a NA twin. In a turbo charged 421, assuming the live engine is producing full power, Vmc would be reached before Vs, the departure here being a roll, not a spin. So perhaps the pilot allowed speed to reduce with reduced power asymmetric.
Typical GA twins will have wing loaded spin characteristics, and a 421B with the main fuel in the tips, even more so. Hence a fully developed spin being flatter, and typically not recoverable.
This link has a nice graph showing the relationship of Vmc and Vs to density altitude.
One engine inop, autopilot on vertical speed, stall and/or vmc roll in imc, game over. Not that one wants to speculate of course…
NeilC wrote:
Not that one wants to speculate of course…
No, of course not, but we have nothing else right now. A C421 with 2 people on board, especially if both of them are sitting in the pilot’s seats, is nose heavy. It should not enter a flat spin. So something must have brought their centre of gravity back – either they had heavy cargo in the back or some lighter load shifted backwards.
Is it only the bad quality of the clip which make it look like there is no vertical stabilizer?