I think Sebastian meant constant RPM, there is no instrument that give you %power on a SEP (or maybe on those MFDs that crunch live data against POH numbers, othetwise one has to think %power = %MP×%RPM×%speed but then RPM is linked to speed with some room for decoupling if you have a VP propeller)
On a piston, torque is proportional to fuel flow, if you are at peak EGT, and then power = torque x rpm x (some constant).
MP is a proxy for torque if everything else is constant.
Indeed the holding power settings won’t work at altitude. For the TB20 it is 18" and 2200rpm, which will give you some low speed, probably about 100-110kt IAS but this won’t work at say FL100, let alone FL200.
Off-topic but interesting Airbus article following the discussion at the end of page 1 and start of page 2 about the limiting factor for max altitude. Obviously, some of the safety factor are for large a/c (FAR/CS 23) and smaller a/c regs might not be exactly the same. But the physic is the same.
Nice article @Xtophe, there are more speeds listed there than the dots you can have on a single PFD !
@Peter, yes external pressure/manifold pressure only give you a proxy for the torque (as you will try max torque allowed by ambiant pressure anyway), are there SEPs where torque or power is actually measued on engine or propeller instead of picked from some POH (+ASI+OAT+ALT) formulas?
On TPs, my understanding this is effectively measured on propellers and pilots will get it displayed and easily do power = torque×rpm…
loco wrote:
before anyone says the plane doesn’t fly its advertised speed at ISA
and the speeds are great. Of course there’s price in fuel for that but the speed and range are remarkable.
