OOW,in answer to your Q about FTH,think of it this way;in an ideal world,ideal engine, on the ground at full power(non turbo/supercharged)( full throttle) you would see a manifold pressure of 29-30"/0 lbs,ie static ambient presure; real life- about 27-28"/-1/2 lbs due to the configuration/losses in the induction system. On top of that, you have a transmission limitation which ,may be 26"/-2lbs,which means you shouldn`t actually use more than that.
Now, as you climb at,say 25", you will need to progressively open the throttle to maintain 25", until at some point the throttle is fully open,or you reach your time limit at max power,and reduce to MCP ,perhaps 23". This may be a transmission limit or engine limit. If you continue to climb,maintaining that limit(23"), you will reach an altitude where the throttle is again fully open, and if you go higher still, the MP will start to decrease. The throttle is fully open ,so there is no restricting of airflow into the carb,which is also doing it`s best to maintain the correct mixture. You can of course still climb,but even with full throttle, MP will be reducing; you may now be only able to maintain airpeed/height at one power setting- more likely you will be anoxic !!
I`m reminded of the Test pilot at Boscombe who was tasked to do a height climb in a Sioux,with oxygen, parachute,etc,who wrote that a stopwatch was irrelevant, a calendar would have been more useful!
2" of MP is approximately 2050 ft in altitude, so you can work the figures for the appropriate aircraft.
If you have turbo/supercharging ,you abide by the same principles,particularly
in helos, since you will have a transmission limit to maintain, but you will still reach an altitude where the throttle will be fully open ,and the boost starts decreasing......don`t forget the calendar, oxygen, blankets etc....Syc
