Referring to DA50 crash: is the austro engine fed by only one single HP fuel pump?
The other worrying feature is the somewhat regular occurrence (possibly annual) of Vmca type accidents (95%+ fatal) in the DA42. Europe/UK in its wisdom (sarcasm alert) still do not apply the safety mitigations applied in the USA for Vmca demonstrations!
What safety mitigations are you referring to?
There are several mitigations:
1. Understand and brief Vsse, which in some types is an actual limitation – EASA/UK seem to be unaware of Vsse (safe simulated engine out speed)
2. Safe altitude, although not much of a mitigant, as the DA42 resultant flat spins are unrecoverable
2. No acceleration into Vmca, ie 1 knot per second deceleration starting above Vsse, wings level maintaining direction control with rudder
3. Recovery at the earlier of a. un-commanded yaw, ie rudder approaching stops, or b. stall warner/first indication of stall
4. Recovery by closing throttle on live engine and lowering the nose
Without the side slip and up to 5 degrees bank which defines Vmca, loss of rudder effectiveness will occur quite a few knots above Vmca. The Vmca demonstration is a recovery demonstration not a test pilot ‘lets define Vmca by seeing how slow we can get to Vmca red line’ exercise.
Most training twins have Vmca proximate to the stall speed, so a yaw aggravated stall ie spin is a real threat, as many ’00’s students/instructors have learnt to their cost.
RV14 wrote:
Referring to DA50 crash: is the austro engine fed by only one single HP fuel pump?
DA50 has CD-300 engine not AE.
The Vsse rarely came up with regards Vmca demonstrtions in any of the twins I trained on including.the DA42. AFAIR we treated them as 2 separte issues and where possible by the book.
VSse was a separate exercise.
For the Vmca demonstration on the DA42 the bôok says not below 3000ft then one engine shut down and reduce speed by 1kt at a time until you run out of rudder on the live side (wings level) the aircraft then turns towards the dead engine so throttle back on live engine nose down to gain speed to Vyse followed by a standard stall recovery to initial altitude and cruise throttle settings. It is not a problem unless you are too low or you allow an accelerated descending turn to set in. In that case you do the same as you would in an SEP eg wings level rudder neutral, throttles to idle, VYse speed and recover as from a stall.
Emir wrote:
DA50 has CD-300 engine
I did have a look at the DA50 POH. The engine is equipped with two fuel pumps, but normal procedure is to use only the main pump. The aux pump is supposed to be turned on only in emergency, after “fuel pressure” warning. Would be very interested in what other more experienced pilots think about this setup.
My understanding is that if the main fuel pump would fail at take off and a pilot wouldn’t react momentarily than EFATO is imminent.
RV14 wrote:
The engine is equipped with two fuel pumps
These fuel pumps deliver the fuel to the (single) high-pressure pump which pressurises the common rail injection system. There is no redundancy for the HP pump.
Correct, only one high pressure pump that, if starved of fuel, can cavitate very easily and then get quickly damaged.
Does the DA42 still have that issue with departing with a flat battery?
