RTA options
Blip,
The info provided is of great value, and I thank you sincerely.
In getting a better understanding of cost benefit in using RTA to absorb some of the delay, (in the cruise mode) can you complete the table below by giving a summary of the fuel used (B738?) for each segment, assuming level flight for each segment?
IAS FL Mach TAS 100 nm in: Time lost Fuel req’d
254 380 .80 462 13.0 min
230 380 .73 425 14.1 min 0.9 min
230 300 .62 367 16.3 min 3.3 min
220 250 .54 325 18.5 min 5.5 min
220 200 .49 300 19.9 min 6.9 min
A similar study undertaken a little while back, using a A310 as the subject, and a 200nm sector requiring an ATC constraint of 45 minutes, demonstrated a saving of approx 600kg when compared with a “standard” procedure of maintaining F390 for 30 min and 15 minutes in the stack at F050 as compared to descending to F250 and min speed for 40 min and 5 min in the stack. The issue is of course, to have in place some form of “contract” that guarantees the slot in the queue when aircraft have conformed with the RTA requirement issued by ATC.
WRT the issue of departure slots, would not the departure window offered by the FMS provide some greater flexibility (for both pilot and ATC) than the current CFMU slot? Assuming a flight of 60 minutes from airborne to RTA WPT (say 120nm from destination), what ‘window’ could be expected?