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.
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.
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 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?
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.
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.
