Absolute Single Engine Service Ceiling

#1
So I feel like a complete dumbass, but I'm not quite sure I've got this calculation down correctly. I remember something from ERAU telling me I'm supposed to slide the ISA line to the right and intersect the red arrows I've put on the attached chart, but I really don't remember.

It's from a Duchess POH, and I'm looking for Absolute SE service ceiling. Did I do this correctly?
 

dc3flyer

Well-Known Member
#3
I started to answer, then looked again... ???????????????

I haven't done that stuff in over two years!! I think the Seminole had a seperate graph, but I'm not sure. It looks good to me though.
 

dc3flyer

Well-Known Member
#5
Calm down man, the MEI was seriously the easiest checkride I have ever taken. Of course, the DPE I used was a "friend" of mine that I sent all my students to, and he may have taken it easy on me.
 
#7
Service ceiling and absolute ceiling are two different things. Absolute ceiling is where you get zero fpm and service ceiling is where you get 50 fpm (single engine).
Right I got that, hence the attached picture shows me trying to figure out at what altitude I would reach the Absolsute SESC. The confusion lies in my methodology in that at my short time at ERAU, they talked about moving the ISA line to find them using a Seminole POH, whose chart differs from the one for the Duchess.
 
#8
Service ceiling and absolute ceiling are two different things. Absolute ceiling is where you get zero fpm and service ceiling is where you get 50 fpm (single engine).
Mmmm I think my wording is what made you say that.

So what you're saying is I shouldn't be calling "Single Engine Absolute Ceiling" what I have been calling it: "Absolute Single Engine Service Ceiling."

Single Engine Absolute Ceiling being the 0 FPM.

Single Engine Service Ceiling being the +50 FPM.

So in other words you're lookin' out for me and teh semantix yo. Thanks man!
 
#9
Mmmm I think my wording is what made you say that.
Yes. I inferred that you might have thought that 8000 ft was an absurdly high service ceiling for a Duchess and hence distrusted your methodology. Sometimes a host of confusion results from a word slip. ;)

I get about the same number you do for the absolute ceiling.
 
#10
Right I got that, hence the attached picture shows me trying to figure out at what altitude I would reach the Absolsute SESC. The confusion lies in my methodology in that at my short time at ERAU, they talked about moving the ISA line to find them using a Seminole POH, whose chart differs from the one for the Duchess.
Oh, make sure you using OAT for the altitude in question. 30 degrees C for 8,000 is really, really hot for that altitude. Perhaps ERAU had you move the ISA line a tool to scale surface temps to standard temperature at altitude. I've never seen that done, but it seems a neat trick.
 
#11
Oh, make sure you using OAT for the altitude in question. 30 degrees C for 8,000 is really, really hot for that altitude. Perhaps ERAU had you move the ISA line a tool to scale surface temps to standard temperature at altitude. I've never seen that done, but it seems a neat trick.
Yeah I was trying to do the same thing with this Duchess chart and it doesn't work out.

And when you say for the altitude in question, I was assuming a 30 degree C surface temp at SL, putting the the Absolute Ceiling at 8000ish. Because I don't know what altitude the Absolute Ceiling is. Should I be doing something different?
 
#12
Yeah I was trying to do the same thing with this Duchess chart and it doesn't work out.

And when you say for the altitude in question, I was assuming a 30 degree C surface temp at SL, putting the the Absolute Ceiling at 8000ish. Because I don't know what altitude the Absolute Ceiling is. Should I be doing something different?
I offer this to you cautiously. I did it in a hurry, 'cause I'm shutting down for the night.
View attachment 3504
 
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