Slow Britannia

[javelin]

OK, we are all sequencing for MAN, I'm 3rd, BY 2nd, LH 1st (obviously got his towel on 24 early).

LH is doing 320, BY claims to be doing 300, I am definitely doing 290 yet I am catching the BY up fast - like from 12 miles to 7 miles between abeam LESTA and DAYNE. End up 4 miles behind on final. LH was pulling away during this time.

Why ?

This happens time and time again, do Boeing ASI's read differently to Airbus ;)

[DFC]

Strong winds today.

What was the vertical difference between you and the one in front? If you were constantly higher (as you would be if further out) then you would have probably had a higher Ground Speed (and TAS).

There is also the posibility of a slightly different track resulting in a) a greather tailwind component for you and extra track miles for the other guy.

Regards,

DFC

[055166k]

Maybe the controller could have used a greater speed differential, but I don;t know the "big picture" at the time. I use a rule-of-thumb 2 per cent per thousand feet when applying speed control. If the BY was 300 knots indicated at [say] 10,000 I would expect the TAS to be 300 plus [10x2=20%]=360.....If you were doing 280 knots indicated at [say] 15000 I would expect the TAS to be 280 plus [15x2=30%]=364. If this job was easy anyone could do it....and as DFC mentioned ....I haven't even compensated for wind in my still-air example.

[javelin]

Good points chaps, the observation we made at the time was that the LH was pulling away and the BY was reversing into us ! I have seen this on several occasions with BY - notable one was 30 miles separation at TOD into PMI - 4 miles on finals. I stayed on standard profile all the way, .78/290/250/210. Perhaps it's an American thing - their knots have got to be bigger than ours haven't they :E