Been doing some maths. Using freely available data concerning the wingspan of a B767, the length of a B737-300 and the physical characteristics of the clearance distances at a licensed airport. I’ve taken the latter from CAP168 Chapter 3.
Firstly the half wingspan of a B767 is 23.8m
The length of a B737-300 is 33.4m
S2 protects Taxiway V so is 47.5m from the TWY V centreline.
Assuming 1m collision overlap 23.0 plus 33.0 = 56.0
Minus 47.5 = 8.5m the length the bmiBaby’s nose may be over S2
It’s a further 75m approximately from S2 to T1 and 75m more to the centreline of 24R
Manchester’s runways are 395.0m apart and Taxiway V is midway e.g. 197.5m from the two runways.
Regarding many posters differing views on what constitutes a clearance maybe CAP 168 helps again.
The Code E taxiway strip should be 95m. Within this area there should be no fixed objects that an aircraft of the maximum wingspan can collide with.
However an aircraft, or vehicle, is a temporary obstacle so cannot be assumed to comply with the foregoing.
If as has been said the crew were cleared to hold at T1 and there was an aircraft already there I would be interested to hear why the crew of the bmiBaby a/c elected to stop 66m, minus the aircraft ahead, from the T1 stopbar.?
This meant that 24.9m of their a/c was inside the taxiway V strip.
No doubt the AAIB will do their usual thorough investigation, however the Swiss Cheese safety analogy is already looming in my mind. Several seemingly unconnected events joining up to breach the layers of defence normally in place.
Some questions.
Could this incident have occurred previously?
If nothing is changed , could it happen again?
What needs to be changed to ensure it won’t?
What parallels at other airports can be drawn?
What solutions on a wider basis can we introduce to reduce the risk?
Sir George Cayley
Last edited by Sir George Cayley; 6th Nov 2004 at 20:17.