Vmc calculation and weight

[172driver]

Shall we turn this into an anti-Riddle (or FSI - which wasn't quite as bad - or anti-Comair or anti-wherever) stage check discussion?

We can if you like but we're talking about the importance or nonimportance of being able to explain the factors of Vmc. The FAA has deemed it to be important so, we as pilots, stage check pilots, CFI's, must ensure that Vmc is being taught and learned in detail. This obviously includes not only the factors but the principles behind them.

The reason we should know how the airplane is configured when certified is that we've got to know how they determined where to put that red line. We need to know that Vmc can occur at speeds much higher than the red line. In my opinion, it's as important as knowing that we can stall an airplane at speeds much higher than the bottom of the green arc.

PTS:

b) Effects of density altitude on Vmc
c) Effects of airplane weight and CG on control
d) Reasons for variations in Vmc
e) Relationship of Vmc to stall speed

 

[100LL... Again!]

172-

You've posted a scenario, but I don't see how you have made your point that knowledge of Vmc factors changes the way the pilot approaches the flight. Also, how do you get such an aft CG with such a low weight? Could happen, but hard to do in most aircraft.

Also, Unless you are carrying bowling balls inthe nacelle locker, I don't think you would likely be able to shift the CG enough laterally to make an appreciable difference.

I think the point you are trying to make is that rudder effectiveness would be reduced, but power would remain the same, plus the laterally diplaced CG, etc could cause Vmc to rise above redline.

Even if the aircraft can produce the same power at altitude (or more, in the case of a Seneca II), the prop efficiency is still reduced. Rate of climb diminishes with altitude even if manifold pressure and rpm remain constant. Your scenario is remotely plausible, but highly unlikely.

Last point: What in the world would anybody be doing flying at redline? (Other than training).

If a pilot does not possess the skill or sense to maintain blueline or better, all bets are off.

 

[Deftone45075]

However, to some degree I think that it is a lo like the old days of airline orals where you had to memorize tons of irrelevant info - such as turboprop gear reduction ratios, etc.

26:1 on the Garret TPE-331's.

 

[mrflyguy]

So if the manufacturer must use minimum weight, what would they use for minimum weight? It seems you could always take a little more fuel out or find a little lighter test pilot.