78X and 744 questions

  • Just a quick post since I'm using the 787 for pretty much the first time, plus something I need to ask regarding the 747 on a flight I did a few weeks ago.


    So first on the 787, is there a way to change the flight number displayed next to the artificial horizon? The FMS seems partially functional on this part as it lets you type in a flight number but once clicking ACTIVATE then EXEC(ute) it does not change. Just asking because the Triple 7 lets you type anything in and it would be nice to have a custom flight number displayed rather than what I've seen so far where it displays UAL123 or BAW787 as a generic flight number.

    Second, I found the 747 struggled to keep speed at high altitude. Just on the Autopilot alone, not the inbuilt co-pilot, I took a Lufthansa 744 from Seattle to Frankfurt and found that at several points during the flight when I tried to get it to cruise higher than let's say 36 or 37,000 feet, it would just end up stalling/getting really low on speed (like 180 to 160 knots indicated, even) and I kept having to enable the GA thrust limit in order to get full power to maintain flight at FL410. Don't know what I did wrong, maybe I put it into the CRZ thrust limit a bit too early but at any altitude from 39,000 to 41,000 feet it just would not keep stable and level flight without becoming dangerously low on airspeed.

    help appreciated,

    thanks

  • The drag curve is U shaped. At low speed you are on the left of centre so a reduction in speed gives more drag. Try going faster to get less drag. You can set up an agressive rate of descent with full throttle and once you are at 290 knots or higher resume the climb but only at a rate that does not lose speed. Above 30,000 feet you are more vulnerable as being Mach limited your Indicated Airspeed will fall with increased altitude and you are moving left on that drag curve. Once you are that high make very small altitude increases to keep the speed up.

  • The drag curve is U shaped. At low speed you are on the left of centre so a reduction in speed gives more drag. Try going faster to get less drag. You can set up an agressive rate of descent with full throttle and once you are at 290 knots or higher resume the climb but only at a rate that does not lose speed. Above 30,000 feet you are more vulnerable as being Mach limited your Indicated Airspeed will fall with increased altitude and you are moving left on that drag curve. Once you are that high make very small altitude increases to keep the speed up.

    Oh okay I see now. Thanks for the explanation.