What airplane is this? (Performance Chart)

[skyflyer8]

Figure 36 from the FAA private pilot test figures. What kind of airplane (if any) does this chart come from?

 

[TMetzinger]

Well, it's a twin that burns 11.5 gallons per side at 65% power, and gives you 165 knots at 8000. Doesn't sound like a seminole to me, but perhaps an early model, or an early Seneca?

 

[AdamZ]

Cougar?

 

[jwriteclub]

I'm probably going to kick myself, but how do you know it's a twin?

~ Christopher

 

[Trapper John]

Well, it's a twin that burns 11.5 gallons per side at 65% power, and gives you 165 knots at 8000. Doesn't sound like a seminole to me, but perhaps an early model, or an early Seneca?

Well, if we take 11.5 GPH and assume 0.42 lb/hp/hr SFC and 65% power, that looks like about a 250 hp engine, which would imply something like an Aztec rather than a Seneca...

But, the really interesting thing is the 2,800 lb weight on the chart. That implies a single, not a twin. Maybe it's an old Comanche 250?

Trapper John

 

[mantakos]

I'm probably going to kick myself, but how do you know it's a twin?

One wouldn't expect a single to have a column that reads "fuel flow per engine".
-harry

 

[jwriteclub]

****.

I should have had a cup of coffee. I was looking at the power/speed charts and thinking that while it would be a peppy single, it would not be impossible.

~ Christopher

 

[Ted]

I dealt with this chart yesterday when I took my written, and had dealt with it during my review using the Gleim software. I, too, got that this was for a twin given the "Fuel Flow Per Engine."

Here's the interesting part - the question on the test assumes that it is a single. How do I know this? Well, they asked for fuel consumed over a trip. If you calculate the fuel consumed assuming it's a twin, the number simply doesn't exist as one of the multiple choice answers. For this I give a thumbs down to the FAA - you would be very unlikely to use a performance chart for a twin when flying a single. At least, not if you hoped to get any meaningful results. The question is confusing, and not in a realistic manner.

By the way, I have no idea what airplane this is for.

 

[TMetzinger]

With that hint from Ted - we should look for airplane families that use one engine in a single, and two of the same engine in a twin version.... Comanche comes to mind, maybe a Bonanza/Twin Bonanza (as a WAG)?

 

[gkainz]

I assume non-turbo, based on manifold pressure drops?

 

[Trapper John]

With that hint from Ted - we should look for airplane families that use one engine in a single, and two of the same engine in a twin version.... Comanche comes to mind, maybe a Bonanza/Twin Bonanza (as a WAG)?

Twin Comanche: IO-320
Comanche: O-360, O-540, IO-540 or IO-720
So, no match there.

Bonanza and Twin Bonanza are very different airframes with different engines, too.

I'm stumped. Whatever it is, it's a pig...161 kt @ 23 gph is pretty sad.

Trapper John

 

[Ted]

I don't see why it should necessarily be from an airplane family that is both a single and a twin. I think all that the hint from me tells us conclusively is that the FAA is using a power setting chart that indicates it may be for a twin, and asking a question for a single engine aircraft. It seems to me the FAA's test question plane may be entirely fictional. If nothing else, having a family that has the twin version go no faster than the single for burning twice the fuel doesn't quite seem right to me - it usually seems that there's at least SOME difference.

My guess is that the FAA just used this chart wrong.

It may not even be for an actual plane... no constructive guesses as to which plane it could be, though.

 

[skyflyer8]

It may not even be for an actual plane...

That's what I'm wondering. Other performance charts on the private pilot test are from actual planes, from what I can tell, such as the C172.

Last night's ground school class subject was performance, weight & balance. Preparing for it is what got me wondering. I was able to tell students how certain charts were from certain planes, but not this one.

 

[Ted]

Kate, I would suspect the performance chart came form an actual plane (Aztec, anyone? It might be enough of a pig to qualify), but the quesiton the FAA asks relating to that chart I would say almost certainly is not referencing a real plane, it is more testing your ability to use the chart.

 

[TMetzinger]

If I was proctoring a test I'd give the student bonus points for raising the questions posted here.

 

[Ted]

You know, the written has a section at the end for comments. I should have made a comment about that, but didn't think to at the time. Oh well.

Tim, if that's your policy you can be my proctor any time.