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I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.Hi Mkloby,
>You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM
Hm, unlike as with some turbine types, on most aircraft piston powerplants engine rpm and prop rpm are directly proportional to each other as they're connected through a fixed-ratio gearing (or directly, in lower powered types). If I mixed the two terms, that would be because they change in unison so that I didn't think of them as separate
Hm, I don't think that we already touched this topic, but increased thrust (regardless how it's achieved) does in fact improve an aircraft's specific excess power, improving its capability for sustained turns.
Instantaneous turns will be unaffected, of course. I guess that's what you were thinking of?
(Just so that the idealized term "instantaneous" won't cause unnecessary confusion: non-stabilized turns of finite duration would actually be influenced by power available
Regards,
Henning (HoHun)
Hi Mkloby,
>You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM
Hm, unlike as with some turbine types, on most aircraft piston powerplants engine rpm and prop rpm are directly proportional to each other as they're connected through a fixed-ratio gearing (or directly, in lower powered types). If I mixed the two terms, that would be because they change in unison so that I didn't think of them as separate
I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.
670 km/h doesn't seem illogical if GM-1 was used, but if the propeller couldn't transfer the extra power then I guess its a moot point.
Hi Vincenzo,
>saw the comparison with P-38-F so encounter only in late '42, i think notleistung was available or not?
Hm, it seems "Zeugmeister" has found some new documents since I last checked this topic ... it looks like Notleistung was cleared with the February 1942 manual: Beim-Zeugmeister: Seite 8 - Flugzeughandbuch der Bf 109 F-4
Attached a comparison based on Notleistung.
Regards,
Henning (HoHun)
The serial number year represents when the contract was issued.why a planes build in '42 have a '43 serial number?
The serial number year represents when the contract was issued.
Because that' the way the contract is let out, especially when large numbers are involved. It actually represents a purchase for the indicated "fiscal year." Although being built in 1942, the aircraft in question was purchased with 43' "money." This will happen with multi-year funding or military equipment.so it's more strange planes build before of contract??
Yes, the contract could have been awarded in that manner.i found that US fiscal year start at october so planes ordered last 3 months of '42 are in '43 fiscal
I'm sifting through various manuals and trying to dig up info...Hi Mkloby,
>I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.
Thanks to Micdrow's and Roy's efforts, we have a great collection of them in the technical forum section
>I confused you with that one, sorry about that - "turns" is a rotary wing slang for Nr (rotor rpm). I was referring to prop rpm there. I'll blame it on the V-22, since we still call it Nr.
Ah, I see! But even then I still don't understand your original comment, I have to admit:
"I am referring to maintaining a specified prop RPM - there is no reason I can see that should cause prop RPM to increase turns, regardless of an increase in engine power at higher engine RPM."
Regards,
Henning (HoHun)
Yes, the contract could have been awarded in that manner.
"Plucked" Part of an original procurement and then re-manufacturerd, I seen either the original s/n used or anothwer one re assignedJoe - there are some strange practices all over the map -
P-51D prototypes USAAF #AC-30479 awarded in 2-27-43 were USAAF serial number 42-106539 and 6740 (THESE TWO were 'plucked' from the P-51B-10NA Block below)
I think paid with 1944 moneyP-51D-5NA, USAAF #AC-40064, dated 4-13-43 were USAAF serial numbers 44-13253 through 44-14052. This is the first block after the two prototypes.
Pot luck!!P-51C-10NT, USAAF #AC-40063 (contract no. PRECEEDING the above P-51D-5NA) was dated 5-3-43 (dated AFTER the above P-51D-5NA).. go figure.
Again "plucking" or remanufacturing of the airframes is my guess.P-51B-10NA, AC-30479, dated 10-20-42 were USAAF serial numbers 43-7113 thru 7202, then 42-106429 to 42-106538 (see two ships above that became D prototypes - same contract), then 42-106541 through 106738.
Hey HoHun,Hi Mkloby,
The propeller could do that, but the engine, geared to the propeller at a fixed ratio, would not run at the optimum speed for the power output selected that way.
If the aircraft had a constant speed prop, the prop gov would seek to maintain an "ideal" prop rpm speed. If the engine is geared to the propeller at a fixed ratio, as you earlier stated, I don't understand how this is possible.Hehe, welcome, but I don't think we've fully exploited the confusion yet
The Me 109 from some version on did in fact have a constant speed propeller.
The desired speed was normally set by a simple analogue computer to match the boost pressure selected by the pilot according to a pre-defined curve. (Maybe more inputs and outputs were involved, but that's the most important thing it did.)
However, if the pilot thought it made sense, he could also flip a switch and operate the constant speed propeller in "dumb" variable pitch mode.)