Or more relevant perhaps, not being built in Belfast

What was "normal procedure" for making good a late time at a turning point? My experience on the JP was in 1970 :)

LingoDan


The time tolerances we worked to in say a Final Nav Test ISTR +/- 6 seconds all using Mk1 eyeball, stopwatch, compass and map (1:50,000 for the IP to target).


There were two options to catch up time; the first obviously was to cut the corner at a turning point or more scientifically, say if say 30 seconds late when planning to have a ground speed of 300 kts, i.e. 5 miles a minute, to increase speed. 30 seconds late meant that you had 2.5 miles to catch up.




How much and how long depended on how long you had left to the target but say it was 10 minutes away, then you could increase speed by 30 knots (an extra 1/2 mile per minute) for 5 minutes to get back the lost time and then revert to the planned speed after allowing for the higher headwind. If you were early due to a tailwind then the amount you had to slow down by could be worked out in the same way.


Obviously the JP only had a limited margin to increase speed so this wouldn't allow for major deviations from plan but you still were expected to try!


I hope that this makes sense - it was over 35 years ago and way before GPS!


MB