Climb Speeds on Short Sectors

[mcdhu]

Can anyone please explain why, in the normal course of events (A320 Series, crz around FL350+, CI 12, mid weight) the climb IAS/Mach will be roughly 285/.77 with the usual crossover level around FL300 and yet on the short flights eg LGW/LTN/STN to AMS/CDG which are capped at FL230, the climb IAS is high - 300ish - which converts to the climb and crz Mach of .65ish at around FL180 so you end up cruising at a ridiculously low Mach No which gives an IAS of around 250-260. I understand why the ac wants to cruise at such a low IAS, but why does the FMGC want to climb at such a high IAS which it then drags back using Mach No to the required low value of IAS.

Cheers
mcdhu

[411A]

Can't refer to other types, however, in the 'ole L1011, heavy weight climbs are always done at a higher IAS, due to the fact that the wing is designed to be much more efficient at those higher airspeeds/mach numbers, at those higher weights.
Same for the 'ole 707, as well.
Once reaching the desired cruising level, the mach number selected, for efficient fuel consumption, is certainly desired.
For the L1011, this would be M.85....for heavy weights.

[Capt Fathom]

For low alt cruise, you normally climb at an IAS that roughly equates to your intended cruise speed.

Climb and cruise at 300 IAS

There is an old saying: climb fast, cruise slow. (But not that slow!) :confused:

[411A]

For low alt cruise, you normally climb at an IAS that roughly equates to your intended cruise speed.

Climb and cruise at 300 IAS

There is an old saying: climb fast, cruise slow. (But not that slow!)

Yup.
In addition, the same is true for large widebody aircraft, flying longer sectors (at higher levels) at a very light weight...ferry, for example.

Instead of climbing normally (250/340/M.835) as you might at heavy weights, a slower climb speed (250/285/M.80) would be desired, and combined with a slower cruise speed (M.81) would demonstrate significant fuel savings.

Fuel...waste not, want not.