durind
Well-Known Member
I have searching the forums and while I have found quite a bit of interesting discussions, I didn't quite find the answer to my question so I am going to post it in here.
So I was sitting my office debating whether or not I should do some more 141 paperwork catchup when our DPE and extremely experienced pilot with other 20,000 flight hours walks by my office and says what have you been teaching people is Vmc in the Apache!? (in a slightly accusatory tone) I respond "72 mph", exactly what the POH says, he agrees and says one of my students was saying it was 59 mph and wasn't sure where he was coming up with this number.
Anyway this leads in to a discussion of Vmc and me basically trying to prove that I'm not an incompetent multi-engine instructor. I mention aircraft weight should be lightest due to the decrease horizontal component of lift when you are banking towards the working engine. He cuts me off, tells me I am wrong and that an aircraft that is heavier has to fly at a higher angle of attack to generate the same amount of lift which increases P-Factor which will be cause the opposite effect of increasing Vmc with an increase in weight. I could see where he was saying and it basically boiled down to me saying I hadn't thought about it like that, and never thought to quantify the forces. Anyone with more experience care to weigh in? He wasn't disagreeing with me, nor I with him but it was a matter of how strong each one of these forces was. A google search has yielded people saying both things, and I'm sure this is something that could vary from aircraft to aircraft, so if that is your approach lets just consider a PA-23-160.
So I was sitting my office debating whether or not I should do some more 141 paperwork catchup when our DPE and extremely experienced pilot with other 20,000 flight hours walks by my office and says what have you been teaching people is Vmc in the Apache!? (in a slightly accusatory tone) I respond "72 mph", exactly what the POH says, he agrees and says one of my students was saying it was 59 mph and wasn't sure where he was coming up with this number.
Anyway this leads in to a discussion of Vmc and me basically trying to prove that I'm not an incompetent multi-engine instructor. I mention aircraft weight should be lightest due to the decrease horizontal component of lift when you are banking towards the working engine. He cuts me off, tells me I am wrong and that an aircraft that is heavier has to fly at a higher angle of attack to generate the same amount of lift which increases P-Factor which will be cause the opposite effect of increasing Vmc with an increase in weight. I could see where he was saying and it basically boiled down to me saying I hadn't thought about it like that, and never thought to quantify the forces. Anyone with more experience care to weigh in? He wasn't disagreeing with me, nor I with him but it was a matter of how strong each one of these forces was. A google search has yielded people saying both things, and I'm sure this is something that could vary from aircraft to aircraft, so if that is your approach lets just consider a PA-23-160.