Having now read the report, I would express some surprise at this runway be suitable for T and Gs with a student, and, in any event.
It is similar in the Citation where runway overrun remains the biggest problem. Once you have touched down, if you don’t like it, do not try to takeoff again – you are just adding energy to the crash. Sounds like a T&G would work but if you end up long you are committed to landing. Clearly that means it is not a strip in that aircraft that is suitable for students.
I was more intrigued about the comments to “set approach flap for short field takeoff” in future – that is not a DA42 published technique that I am aware of?
Not sure about runway requirement for flying twins but a similar risk would have been on a single: all depends on touchdown point, if one comes fast for touch-and-go (or landing) float/bounce for ages and then put full power for takeoff (or go-around) on whatever remaining runway he maybe in a worse situation than fresh takeoff calculation and roll from the start threshold?
I guess there is a cutoff point when to go-around instead of touching the ground for T&G? otherwise cut power and take the loss?
If touchdown point looks beyond 1/2 of the runway, an early go-around before wheel on the ground is the best option
Obviously, kicking touchdown point down runway is “unstable approach” but in nil wind it is something one tend to know about later (it is not just about stable speed & attitude, you also need to kiss where you plan to)
I agree. It is just extraordinary that you would take that on in a twin Diamond. I fully appreciate the safety factors are intended to allow, but even then with its narrow track and, in my experience, far from ideal operating characteristics on soft wet ground it was asking for trouble. I think mixed surfaces are also more difficult because it complicates the abort point on a surface that isnt consistent along its entire length. This way around is even more problematical as there is of course every chance of a dramatic deacceleration as the aircraft passes onto the grass, and is close to rotating, the speed combined with the wet surface makes the chances of stopping even less certain. Oh dear, some suspect decision making I am afraid.
https://www.gov.uk/aaib-reports/aaib-investigation-to-diamond-da-42-ng-twin-star-g-slct
Unfortunate training mishap which fortunately resulted in no injuries. With only 600m of asphalt and winter water logged turf for the remaining 477m, not ideal distances.
With soft ground and public safety factor typical LDR is 550m.
Before any safety factors the TODR is around 700m, and the AFM calls for a 10% safety factor for wet grass, 45% for soft ground and 10% for upslope of 2%. Call me old fashioned but that comes to 1225m. Adding a public transport safety factor takes you to 1600m plus.
I sympathise with the insurance underwriters.
Cobalt wrote:
So is there time to simply pull the power on the good engine, drop the nose and turn into a glider
This is not black and white. You can always reduce power, which will make control easier. If your airfield is at the top of a hill, like Biggin, you might then get back to a controllable speed, feed more power in and climb away.
But in extremis cutting both engines and landing in a field is always an option if things aren’t working out.
I thought posting this ASDR for a Seneca iii might be useful. It’s from the POH so does not have public transport safety factors applied. These would apply to wind and add a minimum of 15% to the TORR. Am not sure what factor they use for the rejected deceleration run. In the absence of VGs (see @Timothy’s post), a dry tarmac runway with a TORA of 1200 metres might apply. Operating off grass would increase this materially.
…. so you say that there is sufficient time to fly to the scene of the crash … 
(sorry, couldn’t resist…)
That is a good point – no need to find the right field immediately, as there is in a single.
But if you are flying at Vx, which in a powerful twin will be not much above stall speed, and below Vmc? In principle, maintaining directional control is not possible with the live engine at full power, so simply dropping the nose and accelerating to above the red line is not possible, it will take too long.
So is there time to simply pull the power on the good engine, drop the nose and turn into a glider (you are no worse off than in the equivalent single), or is the time available too short and you will simply roll over?
Cobalt wrote:
How realistic is it to pull the power on both engines, pretend to be a single and land straight ahead into the next field? You would not be worse off than flying a single.
Funny, the time I shut down an engine I was going through what I would do when the other failed. I would have been happy to land in the same way as any single and would do just that if I hadnt got a positive rate of climb for any reason, although I might hope that the power available might help to adjust the profile, rather than relying on gravity alone to do it for me.
Actually in most twins it is surprsing just how much time you have. Another myth that does the rounds is that you require split second reactions. That is not my experience. The sequence of securing an engine is hopefully smooth and rehearsed with time to establish the aircraft has a postive rate of climb, trim, and settle. There is time to establish the aircraft is still not climbing away and deal with the problem.
