(Peter Stickney) wrote:

In article ,
"Gord Beaman" ) writes:
(Arie Kazachin) wrote:

In message - "Mycroft" writes:

Can anyone think instances when an AC has been push beyond it's limits or
has done things it was never supposed too? The reason I ask is that I
recently read that when Lancasters were carrying Grandslams during WW2 the
engines were seriously over reved at take off because the bomb exceeded the
AC max payload weight by aprox 9000lbs.

Myc


I wonder where people get these ideas?...Lancaster engines (at
least the Merlin 224/225 models) cannot be over=revved (they have
'Constant speed controls' on the props and they cannot be
over-boosted either, they have ABC units installed (Automatic
Boost Controls). So where do these stories come from?...or were
they fitted with some other types of engine?.

Well, with a Lanc, if it wasn't a Merlin 24/224/225, it would have
been a Merlin XX or 22. The only differnece being that the Emergency
adn Takeoff ratings were a bit lower. (Takeoff 3000R/+12 for the
Merlin XX, 3000R/+14 for the 23, and Emergency ratings of 3000R/+14 in
Low Blower and 3000R/+16 in high) They still had the boost controls,
and, of course, the COnstant Speed props.

As for wher the storys come from, they pop up all the time. Somebody
hears something that they think they understand, get it a bit wrong,
and as they repeat it, it grows.

Yes they do don't they?.

As to your power limits for the 224/225 some aspects don't look
as I remember them. (Now take note that this was nearly 50 years
ago so cut me some slack) I thought that the max RPM was 2900
(remember that I have some 16 years on R-3350's with 2900 RPM
limits so this might be the reason that I think that). Also I
know that the max boost was 18 in low blower. I don't remember
what the boost limits were in high blower but it seems odd that
they'd be _higher_ than in low. So as not to mislead you about
those power limits I have two old F/E friends here in town who
flew Lancs so I asked both of them just now. One isn't sure of
the max RPM but 'thinks' that it's 2900 and the other is 'sure'
that it's 2900 and they both agree with me about the boost limits
which were 9 pounds (at the 'gate'), 14 pounds at full throttle
and with the 'boost over-ride' pulled (which cut out the
Automatic Boost Control - known as 'pulling the tit') gave ~18
pounds.

I realize that you're a damned fine researcher and have a lot of
facts at hand and I feel a little timid about 'instructing' you
but I'm very sure of my facts about these a/c. I logged 575 hours
as F/E on them.

They were Lancaster X (MR) with Merlin 224/225 engines as used by
the RCAF in Canada for ASW work in the early to mid fifties and
replaced in (I think '55) with Neptune P2V-7's (with no jets
installed until later).
--

-Gord.