RobertL18C, nope, there’s no regulatory requirement to include ASDA tables in the AFM for a Perf Class B aircraft (as indicated in the linked discussion). Older models PA31 etc still have such tables but aircraft such as the DA42/62 don’t (in my opinion, a backwards step).
For Commercial Air Transport the European requirements (CAT.POL.A.305) for a Class B aircraft are that unfactored TODR in the AFM when multiplied by 1.25 shall not exceed the TORA.
Alternatively, if there is a stopway and/or clearway available the unfactored TODR:
a. shall not exceed TORA and;
b. when multiplied by 1.15 shall not exceed TODA and;
c. when multiplied by 1.3 not exceed ASDA.
Mooney_Driver wrote:
hen again, looking at some unbalanced take offs I’ve seen in my time e.g. by the old Pan Am 747-100 series out of ZRH
Are you even allowed to do that with Transport Category aircraft?
Fuji, we crossed.
What would I do? I would treat the aircraft like an SEP that had just lost it’s engine! One of my niggles is the ATPL schools peddle the message that multi-engine aircraft can be operated safely at any point; it is simply not true as we have previously discussed.
The EFATO decision in a Class B aircraft is more complex than Class A and fundamentally revolves around controllability. There is no V1 decision – if you are less than Vtoss you’re staying down and if you’re above Vtoss you will probably be airborne (we could have a long side-discussion about taking-off at speeds higher than Vtoss to mitigate the danger zone)
So, from a piloting perspective, let’s assume we’re above Vtoss (ie airborne) and an engine fails. For ease, I’ll thrown in some numbers which reflect the DA62
Vmca 70
Vtoss 78
Vx & Vy 86
Vyse 89
In this particular aircraft, your focus is on achieving Vyse which you should be well on the way towards as soon as airborne. The reality is that a very slight reduction in pitch attitude and retraction of the undercarriage will achieve Vyse within a matter of seconds; raising T/O flap is a bit of a moot point as you will sink a bit. I think that you would be extremely unlucky to have a failure at 79kts and then lose the ability to reduce drag (raising gear) thus finding yourself down in Vmca territory. If, and its a big if, your airspeed is winding off towards Vmca then your only option is to retard both levers and become a glider. There are more than enough youtube videos of Vmca nasties at low level.
Looking at another aircraft such as the PA31, your theoretical exposure is higher.
Vtoss 85kts (76kts with T/O flap)
Vmca 76kts
Vyse 106kts.
So here you’ve got to work harder to get to a best climb speed (remember, Vyse is best single engine rate of climb, you may well still be able to climb at higher/lower speeds). However, the principle is the same, get rid of drag, get towards Vyse and take things from there. Your worst case scenario here is a failure immediately after a short field take-off as you are pretty much already at Vmca. So, as before, your only option if you cannot create an environment where you are accelerating is to retard the throttles and give yourself a controlled crash, a la SEP.
Risk – Timothy has said it numerous times before and some repetitive offerings:
Engines rarely fail. A catastrophic failure resulting in an immediate loss of all power is even more rare.
Your exposure time between Vtoss and getting to Vyse is very short. Assuming you only have an engine failure and you can clean-up/secure the engine, the time period is somewhere in the region of 5 seconds for a DA62 and maybe 10 seconds for a PA31. Again, you’ve got to be really unlucky for the engine to let go in these few seconds.
A look at engine failure crashes in MEPs will probably demonstrate a high percentage of crashes occurring in the second/third phase of flight. People rushing, turning towards dead engines, turning base/final too tight etc.
Sorry for rambling but the simple answer is if you heading towards Vmca and cannot reverse the trend, throw away the aircraft in a controlled fashion.
One of my niggles is the ATPL schools peddle the message that multi-engine aircraft can be operated safely at any point
Not true in the case of Performance B puddle jumpers – the student has to memorise a take off brief which is clearly designed for the shortcomings of MEP. Fortunately they move onto Performance A types after a couple of months.
Dave – that seems to me very well put, thank you, and you raise and interesting point
Dave_Phillips wrote:
(we could have a long side-discussion about taking-off at speeds higher than Vtoss to mitigate the danger zone)
which would be an interesting discussion given that you may well not have distance to stop unless you are as cautious as Timothy 
or arguably if you dont like whats beyond the upwind threshold, for example some City airports.
Thoughts on that matter?
RobertL18C wrote:
Not true in the case of Performance B puddle jumpers – the student has to memorise a take off brief which is clearly designed for the shortcomings of MEP. Fortunately they move onto Performance A types after a couple of months.
Indeed, it shouldn’t be true but I’ve sat with fresh CPLs from the following schools over that past year and they basically don’t have a clue:
FTA
Aeros
SFC
Don’t even get me started on memorised take off briefs. They rattle them off like the Lord’s Prayer; something most of us learnt when we were in shorts and can recite at the drop of a hat without a single thought.
Fuji, in the two aircraft I fly I don’t play around with Vtoss for the DA62; it isn’t worth it as the necessary speeds are comparable and arrive so quickly.
The PA31-350 is a different beast. In general terms, I think most of us trade height for speed and, on a runway that isn’t limiting, will probably rotate a little after Vtoss. Interestingly, the PA31 AFM also indicates an ‘accelerate to 92kts’ before pitching-up on a normal departure EFATO and I suspect this reinforces the preference to get some speed before height.
For the PA31 I will always try and avoid the short field option for two reasons. Firstly, the 9kts difference in Vtoss, combined with the drag induced by flap will make things more sporty in EFATO scenarios. Secondly, if we look at the worked examples for departures in the PA31-350 manual you get some very interesting results. For a short field take-off you will be airborne in1150ft and reach screen height (50ft) in 2200ft (they use a lightweight aircraft for the example!). Under exactly the same conditions (weight, temp, pressure etc), a normal take-off will use 1240ft but reach 50ft after 1880ft. This really highlights that short field techniques are only of use on genuine short runways and it is alway best to try and fit the normal departure profile.
When training, I encourage the junior pilots to get out of the red-line-to-blue-line arc territory with alacrity and I suppose this does come at the expense of some height.
Interesting subject as I just got my MEP on a DA42-135. I find rather short to be granted on MEP with just 6 hours (half on assymetric flight and failure management), given the higher complexity, and especially the critical instants when you are on takeoff after Vr but below Vyse.
Dave_Phillips wrote:
Don’t even get me started on memorised take off briefs. They rattle them off like the Lord’s Prayer; something most of us learnt when we were in shorts and can recite at the drop of a hat without a single thought.
We do have to briefing we kind of mostly do by heart, and I see that you are not liking ot too much, but as soon as you don’t fully integrate it – and experience it -, you need to be prepared…
This been said, on DA42 (not NG), you takeoff flaps up, which is apparently not the case for DA62.
greg-mp, don’t get me wrong, the crew departure brief is essential but it needs to be heard and not just recited with no thought.
Yes, the 62 gives you the option to take-off with or without flap.
Pilot_DAR wrote:
On this topic, I like this article:http://www.cfidarren.com/p8740-25.pdf local copy
This text is gold! Thanks a lot.
