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Haven't we been through this? I explained how I calculated it. The time to climb figures came from the Hurricane Mk.I page on https://www.wwiiaircraftperformance.org. The time to climb figures I simply calculated the time to climb based on the altitude change (i.e. 1000-2000, 2000-3000, 3000-5000, 5000-6500;, 6500'-7600').Your calculations ???
No, I was using their figures. The fact was that the climb-rates listed didn't match up with the time it took to get to the given altitudes.My apologies Zipper730, like tyrodtom I also thought that you were quoting values calculated by Hawkers or some other agency back in the 1930s. I did not realize that you were asking why your method was not working out.
That's correct, but I was using the time between altitude intervals. It was the best precision I could manage, and the figures didn't add up.In addition, imprecision in measurement (ie misreading of instruments), and/or imprecise or miscalculation, and/or typos, by the agency responsible will mess things up. If some of the numbers are rounded off or are imprecisely measured or typoed (even by only a few hundredths of a minute for example) then any later calculations using smaller increments than originally used will result in exaggerated variance from the original result.
Wait, I thought the limitation was set by boost rather than HP?The reason I suspect the 2976 ft/min average ROC value is still incorrect is because with the British method of using constant boost to FTH (rather than the US method using constant HP) the instantaneous ROC at FTH has to be higher than the average ROC anywhere below FTH.
Yeah, I figured you'd see a constant boost setting up to the critical altitude, with an increase in horsepower up to that point due to a throttling loss.The UK used constant boost pre-war and early-war, at least for the aircraft fitted with constant speed propellers. They used it for most of the rest of the war also.
The Hurricane prototype (where I got this data from) seemed to include a progressively increasing rate of climb until critical altitude is reached.On the climb chart HP is controlled by boost at +12 lbs to FTH for the Normal climb rate and +16 lbs to FTH for Combat climb. In both cases the climb rate increases slight from SL to FTH, giving a line that slants to the right as altitude increases to FTH.
That's pretty odd. Throttling loss would occur most at low altitude, then go away at FTH. It seems with a setting like that, you'd be underperforming quite a bit.The US used torque meters on their engines, from pre-war, to prevent generating more HP than one part or another of the engine could sustain safely. In effect the US used a fixed BHP as the limiting factor. If you look at some of the US engine charts, the boost will decrease slightly as altitude increases, upto the altitude at which the max safe HP can be generated.
I figured the T/O setting was the same as the maximum setting. Military power is usually a little lower (usually it's emergency power, military power, and normal rated), but I see what you mean.Note the boost at Military at 11,800 ft FTH and at TO at SL. Both ratings are 1150 HP at 3000 rpm.
That's a good question, eventually the V-1710 would be beefed up quite a lot. W wuzak , do you have any figures as to engine strengthening throughout WWII?I have read that reduced pilot workload was the main reason the UK adopted constant boost as the limiting factor. I do not know for sure that this is true for the US, but I would guess that it was. Whether this was also due to sturdier models of engines, or the recognition of already existing strength in the engines, I cannot say.
I have read that reduced pilot workload was the main reason the UK adopted constant boost as the limiting factor. I do not know for sure that this is true for the US, but I would guess that it became so as the war progressed. Whether this was also due to sturdier models of engines, or the recognition of already existing strength in the engines, I cannot say.
Sag in the middle? It just seems to curve up and to the left instead of form a diagonal line to the right.One way to estimate the TTC value for climb to Service Ceiling (SC), and any altitude in between, is to figure the average ROC from SL to FTH, and then do the same for FTH to SC. The resulting ROC curve should be a nearly straight line from SL to FTH (regardless to using boost or BHP as the limiting factor - if boost is the limit then it will lean to the right, if BHP is the limit the it will lean to the left). The precision calculated line from FTH to SC should also be a nearly straight line (but not as straight as the line from SL to FTH) with slightly convex curve (ie sag in the middle).
That's what I was under the impression of as well. And yet they were pulling back a skosh as they went up. I'm not sure if this was to correct for ram or something.Boost wasn't really constant, but rather a boost limit. The boost was maintained as constant to the full throttle height, after which it would fall off.
That's what I was under the impression of as well. And yet they were pulling back a skosh as they went up. I'm not sure if this was to correct for ram or something.
It was a sinister pre war tactic to get one over post war internet discussion forums, the lizard shape shifters were behind it mainly inspired by Prince Philip, all well documented and proven by science.Who was pulling what back? A
And what the fuck is a "skosh"?
closely related to but not identical to a "smidgen"And what the fuck is a "skosh"?
Hey wuzak (and others),
re: "Automatic boost controllers were adopted to ease pilot work load, these were used whatever the boost pressure was set."
My understanding is that automatic boost controls were mostly used to prevent overboost as an aircraft descended, ie for example a pilot might increase boost to max at 7600' when entering combat and in the ensuing maneuvers descended to SL. At least the in the early-war. Were they used/operated differently later? I am not particularly familiar with the various mechanisms used by the different nations, so any info would be appreciated.