Answer this toughie

[stuckwithmassey]

We all appreciate that an aircrafts (in this case Jet) best rate of climb speed occurs where excess power avalible occurs.
What happens if the aircraft is now considered heavier?
From looking at power avaliable and power required graphs i figure that seeing drag increases, so to does the new best rate of climb speed.

Any jet pilots able to help me out??

[Wizofoz]

swm,

Yes, you've got it in one. Best ROC speed increases with increased weight.

[slice]

This is correct and doesn't only apply to jets - all ac have varying best ROC airspeed that varies with weight - though in single engine piston ac there is usually not much more than a few knots in it.

[stuckwithmassey]

hey thanx guys, was just unsure due to the lack of literature on it.

[MoFo]

The report on the Concorde prang in Paris gives a sad example of drag vs thrust when you try to fly a delta wing at an airspeed below V2.

If you can get a copy of the accident review you will see that it was never going to climb at that speed. Very sad occasion.

[Boomerang]

Putting theory into practice, when (what altitude) does your Vy become a mach number, or is it never a factor?

(I'm not a jet driver so I don't know if you ever climb at Vy up that high, unless you wanted max alt?)

[DirectAnywhere]

Boomerang, given that the speed varies with weight, the altitude at which Vy/ Vx will correspond to a Mach number will also change.

For the aeroplane I fly, if your target altitude is within a few thousand feet of cruise altitude, best rate/ angle will be achieved by a normal climb profile.

Vy will typically be well below normal climb IAS and often factors such as Vimd would limit the practicality of an "My" or "Mx".

And swm, try "Handling the Big Jets". Great reference for jet aerodynamics and handling considerations.

[Feather #3]

Boomerang,

Between about FL280/290 for the B747 series.

G'day ;)

[readbackcorrect]

yeah i understand that the Tas or Ias for Vy decreases with altitude. The speed of sound also decreases with altitude/temperature. So by selecting the appropriate Mach number will ensure that the IAS reduces as u climb to equate somewhere around Vy.

Yeah thats right Vy is seldom used cos its too slow.

[Lefthanded_Rock_Thrower]

This is because the Power Required curve moves up and to the right.

the IAS changes with altitude, as the ASI is not accurate and we do not have angle of climb indicators, the VY is in its rawest terms an angle of attack.