Id typically go with the most common figures for anything. Simple strenght in numbers.
Which is better: P-47 or Fw-190?
- Thread starter mosquitoman
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Often, the most common figures cited in published sources are derived from the same "other sources." (We've all seen erroneous figures relied on and published in multiple venues.)
That' why primary source documents are so important. The chance that the Army Air Force's own flight manuals would be based on erroneous data is mitigated as the Army Air Force is the primary and direct source repository of the data itself.
There is no chain of custody issue to deal with where a figure is based on a source that is cited from another source that purports to be based on official primary source data. The Army Air Force doesn't have to search the "web" and books for data to base performance figures on. They merely consult the original data that was collected.
The Army Air Force is also in the best position to catch and correct mistakes either clerical or substantive in nature. Manuals aren't released without creful editing for errors and substantively erroneous data is caught because it is the Army Air Force that uses that same primary source data in determining and checking performance data in other tests. For instance, a substantive error that places a wing loading at 40lbs is more likely to raise eyebrows when actual performance tests indicate that it ought to be 35lbs.
That' why primary source documents are so important. The chance that the Army Air Force's own flight manuals would be based on erroneous data is mitigated as the Army Air Force is the primary and direct source repository of the data itself.
There is no chain of custody issue to deal with where a figure is based on a source that is cited from another source that purports to be based on official primary source data. The Army Air Force doesn't have to search the "web" and books for data to base performance figures on. They merely consult the original data that was collected.
The Army Air Force is also in the best position to catch and correct mistakes either clerical or substantive in nature. Manuals aren't released without creful editing for errors and substantively erroneous data is caught because it is the Army Air Force that uses that same primary source data in determining and checking performance data in other tests. For instance, a substantive error that places a wing loading at 40lbs is more likely to raise eyebrows when actual performance tests indicate that it ought to be 35lbs.
I will agree with you here, the best souce is the direct manual itself.
wmaxt
Staff Sergeant
Of course the data in the flight manuals is also "Hedged" or conservitive so that an average pilot in an average plane with average maintenance and flight hours can expect. For example in the P-38 manual the highest power setting shown for a L model is 1,600hp @ 60"hg, even though at 64"hg it could pull 1,725hp.
Two profiles are shown for climb performance, Ferry and Combat climb. Combat Climb is only 1,100hp (CORRECTION 54"hg is 1,425hp) @ 54"hg and 3,000 rpm (METO power not normal) the climb is at optium climb angle for 3,200ft/mn initial. these numbers are not even close to the maximum available.
Also all, time, numbers are rounded for simplicity
So yes the manuals are great sources but may not be difinitive either.
wmaxt
Two profiles are shown for climb performance, Ferry and Combat climb. Combat Climb is only 1,100hp (CORRECTION 54"hg is 1,425hp) @ 54"hg and 3,000 rpm (METO power not normal) the climb is at optium climb angle for 3,200ft/mn initial. these numbers are not even close to the maximum available.
Also all, time, numbers are rounded for simplicity
So yes the manuals are great sources but may not be difinitive either.
wmaxt
The manuals normally show the safe operating limits.
wmaxt
Staff Sergeant
DerAdlerIstGelandet said:
Thats true. It's also true that performance figures are "averaged" to fit aircraft in normal (not new) condition. The limits are also fudged for purposes of economy in peace time as well. I have a 1954 t-1 flight manual for the P-51 and there are a number of perameters that are lower than combat conditions would even consider.
If a pilot jumps in his plane and can exceed the flight manual a bit he's going to be very happy with his aircraft. If he jumps in and can't achieve his expectations you will have a pilot who detests his aircraft and the maintenance crew he bets his life on. As you point out the safe operating envelope is listed but it must also fit the average age and maintenance of the aircraft. Last the data must be reliable enough to allow mission profile and planning to be acceptable for all the aircraft involved, even the one in the poorest condition. Things like range can be dependant the pilot/outside influences.
All I'm really saying is that the flight manual is a good place to start defining the normal performance envelope of an aircraft but it will not give you the maximum performance envelope. It's dependent on too many things.
One thing we all do here is use new/optimum figures to compare aircraft. There are to many variables to compare anything else but we need to keep that in mind.
wmaxt
You also have to remember that the aircraft could exceed the normal limits anyhow, well atleast if the aircraft was maintained properly.
wmaxt
Staff Sergeant
DerAdlerIstGelandet said:
Exactly
wmaxt
wmaxt said:
True to this also.
Yes but what we are saying is the Owners Manual only tells you the safe operating procedures. Normally there is an appendix that will tell you the max limits of your aircraft but the normal performance values and limits are for safe operation.
Atleast thats the way it is with my aircraft and the other aircraft I have delt with.
Atleast thats the way it is with my aircraft and the other aircraft I have delt with.
Sal Monella
Airman 1st Class
I'm not sure I understand. Are you saying that actual test data for maximum figures would be higher than performance figures in a manual?
Nonskimmer
Captain
Quite possibly. Manuals will normally list nominal performance characteristics only. This hopefully keeps the operator from doing something foolish, but it's good to have the added capability that comes from a well built, well maintained machine.
the lancaster kicks ass
Major General
- 19,937
- Dec 20, 2003
but remeber as well that it was uncommon for planes to fly at full power for any realy length of time, we talk about planes speeds using their top speeds when they would very rarely hit this........
To reiterate, "While it is true that performance figures in pilot flight manuals can be "underrated", the weight figures in such manuals shouldn't be rated lower or higher than usual."
To the extent that they should not be lower or higher, they would be accurate. And following this, should be accepted as accurate.
To the extent that they should not be lower or higher, they would be accurate. And following this, should be accepted as accurate.
DAVIDICUS said:
Yes it would seem that way, but its hard to believe that so many researchers got it so horribly wrong though. Something is fishy about that manual....
Anyway, if the manual's weight figures are correct then the -47N 'should' be climbing at something like 3,450-3,500 ft/min, the same as the -47M. And if the figures aren't correct, well then it would most likely be climbing at something like 3,150-3,200 ft/min.
FLYBOYJ
"THE GREAT GAZOO"
Soren said:
This was discussed in another thread. Sometimes engineers place between 2-5% "governor" factor in some aircraft performance numbers, just so if there is an expedience, the plane isn't being readily destroyed.
FLYBOYJ
"THE GREAT GAZOO"
Soren said:FLYBOYJ said:
Which has what to do with "weight" figures ?
We're talking weight figures here, not engine performance figures
Sorry my mistake, but I would also add weight to that factor. Look at aircraft weights and maneuving speeds. The heavier the aircraft is, the more it rough air penatration and Gs it could take. This is shown in the -1s. I would think that engineers would factor these numbers in so a pilot won't takke a lightly loaded aircraft and start putting excessive Gs on the airframe.
