Single engine climb speed (piston)

[compressor stall]

Chasing prawns around the Gulf for 5 hours a day has allowed time for word for word perusal of
flight manuals, and subsequent contemplation of the above question. Infrequent rural internet access has
prevented my earlier reply here.

My thoughts agree with John_Tulla's. Some of what comes under repeats his statements above, but I am cutting and pasting what is on my laptop so forgeive me.

First, the fact that the aircraft is asymmetric is irrelevant - it is basically
equivalent to an inefficient underpowered single...

As for aircraft specifics, both the AC50 and the C310 have airspeeds (CAS and IAS respectively)
listed in the flight manual which decrease with altitude at the rough rate of a couple of knots for
a couple of thousand feet

Grab a pen and a blank piece of paper...and start with the power on the y axis and
TAS (note TAS) on the horizontal.

Best rate refers to excess power (as mentioned above).

Draw the best power required graph (the flattened J shape) for sea level.

Now an increase in altitude will require an increase in TAS for steady level flight. The effect of this
will move the curve upwards and to the right but not change its shape. A point on the altitude curve (corresponding to best range, but that is irrelevant) is still a tangent from the SAME line from the origin. Draw in this curve (in red) upwards and to the right (imagine "sliding" it up along the tangent line.

Draw in the power available graph (upside down flattened "n") for sea level.

The effects of altitude will reduce the power available, pulling the graph vertically downwards. Draw this new position (in red).

Now the maximum excess power at altitude (between the red curves has reduced significantly (to be expected and resulting in a reduced rate of climb) but it has shifted to the right - to a higher TAS.

As altiude increases, the difference between TAS and IAS/CAS increases. On some aircraft, the TAS increase is so slight over the change in altitude, that the corresponding IAS is actually
decreasing. In a climb at a constant TAS the IAS decreases by such a rate that it must be possible to have a slight increase in TAS and still maintain a (reduced) decrease in IAS.



Apologies for the layout - it was a notebook document!