# How to work out speed for flight

## Recommended Posts

So I have setup a route from EGLL-KJFK and I have fuel and such planned. I have the v1 VR and V2 speeds but idk what speeds Id use for climbing, cruising, decent and final. I use a BA 777-200.

Any advice how to work them out for the flight?

##### Share on other sites

Use .70M for the climb, cruise nominally at .78M to .82M, descend at 280Kt - 290Kt or .72M, final depends on weight ... if you are using the PMDG aircraft all of this is computed automatically.

DJ

##### Share on other sites

• 2 weeks later...

Typically airline pilots don't switch over to Mach until reaching "crossover" altitude, where CAS and the desired Mach value represent the same TAS value. For example, if you're climbing at 280 kts and you want to reach Mach 0.74 at that constant speed you would have to climb to FL298 to have 280 kts equal Mach 0.74, so the crossover altitude is FL298

This crossover altitude varies with atmospheric conditions, etc., but, at least in my experience, it usually occurs for me between FL266 and FL280 where 300 kts = Mach 0.74--usually right about FL275 on relatively calm days.

On most of my flights in my 747s I'll increase my airspeed to 280 kts once I pass 12000ft, 290 kts at FL180, and step-climb at 300 kts as I pass FL240 to around FL275, where, when switching over to Mach, my indicated Mach speed is 0.74/300 kts. From there I'll step-climb to my cruising altitude, decreasing my rate of climb as I ascend to keep my N2 below 88%, and depending on wind conditions cruise at Mach 0.82 to Mach 0.87.

I could use cruise climb to reach my target altitude, but I've found that in FSX, if I step-climb I save several thousand pounds of fuel over the long haul, versus a sustained cruise climb, which seems to burn more fuel per engine, per hour. FMS computers do take care of all of that, but I'm old school and like to do those calculations myself. ;)

I got those climbing parameters from watching videos of airline pilots who fly 47s out of KLAX. The numbers certainly aren't set in stone, or anything like that, to be sure, but they definitely work for me in FSX. :)

Happy flying!

APUtech

##### Share on other sites

Those speeds should show up in your FMS climb pages.

You'll max out at 250 kias while under 10,000 feet. After that, your FMS flight plan should automatically transition you to your target climb speed.

RalphF

##### Share on other sites

I was an FE on an L-1011 and flaps up min speed was well under 250 kias. I flew in the jump seat on the DC-10 and the B-747 many times and after TO, with flaps up, we never had to fly faster than 250 kias to stay in the air.

I'm not sure where you got your information from, but its wrong.

RalphF

##### Share on other sites

I was an FE on an L-1011 and flaps up min speed was well under 250 kias. I flew in the jump seat on the DC-10 and the B-747 many times and after TO, with flaps up, we never had to fly faster than 250 kias to stay in the air.

I'm not sure where you got your information from, but its wrong.

Agreed, rfresh737. A 747-400 can fly near 190 kts without flaps in level flight. In fact, on a typical apph here to my hometown airport KSAN the British Airways 747 that lands here every day doesn't start extending its flaps until it's about 5 to 7 miles from touchdown (I live less than a mile south the final apph path to Lindbergh rwy 27, east of the REEBO int and spend some free afternoons plane-spotting, binos in hand).

Happy flying!

APUtech

##### Share on other sites

rfresh737 thinks that your info is wrong, because it is.
##### Share on other sites

I am not a pilot by any means but I switch to the Mach after 26,000 feet and in over 20 years with Flight Sim ,,,never experienced any problems...also change the altimeter at 18000 feet or the warning light appears in the upper left screen on my stuff..
##### Share on other sites

@bbrz might not be wrong. I'm only going by my flying experiences. When flying the L-1011 as an FE I can't recall ever having the flaps out when we hit 250 kias on climb out. When I flew the jump seat in a B-747 on a non-stop flight from Los Angeles to London (12 hours), the flaps were up when we reached 250 kias. If I recall correctly, we were not at full gross weight on TO, but we were certainly heavy.

There might be some situations where clean configuration put you over 250 kias, but I think, based on my experiences, those are rare.

RalphF