Semaphore_Sam,
If you think that the 400 is strange just wait until you move to the pocket rocket.
I am extremely disappointed that no one has explained this to you in recurrent
, In JT’s comments above he compares an aircraft to a boat, this is rather simplistic but true, as the depth of contaminant increases it reduces the aircrafts acceleration but greatly aids the aircraft’s ability to stop.
The following are an approximation of the acceleration rates.
Dry - All engine acceleration = 3.5 kts/sec
Dry – One Engine Inop acceleration = 2.3 kts/sec
6 mm – One Engine Inop acceleration = 2.0 kts/sec
13 mm – One Engine Inop acceleration = 1.5 kts/sec
From this you can easily see that 13 mm of contamination is worse than 6mm, but then we have to look at stopping….
Dry – One Engine Inop deceleration = 8.0 kts/sec
6 mm – One Engine Inop deceleration = 3.0 kts/sec
13 mm – One Engine Inop deceleration = 3.5 kts/sec
Your takeoff weight is a trade off between the accelerate go and the accelerate stop, with the greater stopping ability associated with 13mm you will usually see better weights!
As for the FAA certification, I’m at a loss as to how they have avoided this subject for so long. I guess that it just doesn’t snow in North America.
Cheers.
Mutt.