Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Hello, folks,
As noted in another thread, the Melrlin 45 was over-boosted in 1942 (+16 lbs/sq in, previously only 9,3 lbs/sq in). Flight tests with over-boosted engines were conducted from July to September of 1942. So, my questions are: was it feasible before that date? Does anybody know what major/minor changes on the engine were undertaken?
The benefits of the over-boosting were noticeable mostly at lower altitudes, where that improvement was feasible anyway. The full throttle height for that rating (noted as 'combat rating') was, on climb, 8800 ft, and, at max speed, 13000 ft. The speed gain was, on 13000 ft, 35 mph, and the RoC was increased, at 8800 ft, some 1050 ft/min (now being 3710 ft/min at that altitude).
Care to point me to an easily accessible source?
Thanks, I'm aware of that. However, I'm after the Merlin 45 data
That is not in agreement with 'The Merlin 45 always had 12lb overboost' statement; the report covers the results of the test being done between July and Sept of 1942, while the M 45 was in use a full year (or more?) before that.
The Ministry of Aircraft Production letter says the Merlin 45 was "introduced" with 12lbs boost, and that's dated 3 January 1942.
Thanks for the feedback. Is there some info about the steps taken to ensure that the M 45 was working properly at +12 lb boost, and later at +16 lb boost?
I don't quite understand what you are trying to ask. Are you asking what modifications were made to ensure that the engine could run reliably at 12 and 16lb boost?
Yep, the data can be easily found at the Mike Williams' site (Hurricane II can use higher boost for the low gear, but not tat high for the high gear).
That's what I'm trying to find out
There was nothing preventing pilots from using the Merlin XX with 12lb boost, even in high gear. I'm fairly certain that advisory warnings not to do so, went out the window in life and death situations.
The same site has this article:
http://www.wwiiaircraftperformance.org/merlin-lovesey.pdf
which is an excellent summary of Merlin development and mods required for higher boost.
BTW, the chart (fig 24) on page 223 of Lovesey states that the Merlin 45 was approved for 16lb in late 1941 (same time as Merlin II/III).
Thanks for pointing me to read again the Lovesey. If I'm reading the available data right, it took from late 1941 to July of 1942 to start flight tests of the M 45 at +16 psi, while the results were issued on 25th Nov 1942?
As for the limitation for the Merlin 20 series, it took until late 1942 to cancel the limitation (allowing the + 14 and +16 psi for high gear).