Pearl Harbor Defense

Chris Mark wrote:

From: Guy Alcala

in 1941,
they started to see just how much they could safely stretch the fuel economy
of the Zero, individually and then in larger groups. Ten hour missions
became routine, then 11 and eventually they were able to stay in the air for
12. Okumiya describes this in "Zero!", with average fuel consumption
dropping to 21 gal./hr. and Saburo Sakai holding the record at only 18
gal./hr.

Interesting. The Wright R-2600 engine burned about 75gph at 60 percent power.
Any details on how the Japanese achieved such frugal fuel consumption figures?
What was "normal" fuel consumption for the Zero?

I have a vague memory of reading 30-35gal./hr. somewhere, but don't hold me to
it. The A6M2 had the Sakae 12 engine, which was only rated at 950 hp or so. When
they got the A6M3 Model 32 in the Solomons, which had the more powerful Sakae 21
engine of 1,130 hp (and slightly less fuel) plus clipped tips, they found that its
range was inadequate to make it from Rabaul to Guadalcanal and back (it was
pushing it for the A6M2), which IIRR was something like 550 sm one way. They
built intermediate strips down the Solomons (Buin, etc) so that it could get there
and back, and put the A6M3 Model 22 with increased internal fuel and the full
wingspan (non-folding, like the first production model, the A6M2 Model 11) into
production for land use.

The USN found that for carrier operations, overall they could plan on R-2600s
burning 45-50 gal./hr average per sortie (which includes lots of low speed loiter
for landing and ASW patrol) depending on whether it was in an Avenger or a
Helldiver, while the R-2800 in the Hellcat burned about 75 or so (same landing
loiter, CAP loiter). The exact mix of sortie types flown would affect the
average, but as far as planning for carrier AVGAS replenishment needs, that gave
them good numbers.

Guy

From: Guy Alcala

What was "normal" fuel consumption for the Zero?

I have a vague memory of reading 30-35gal./hr. somewhere, but don't hold me
to
it. The A6M2 had the Sakae 12 engine, which was only rated at 950 hp or so.

So by using the standard procedures outlined by Mr. Stickney, they were cutting
normal fuel consumption by about a third, which sounds right. There used to be
a belief in the long ago that low rpm and high manifold pressure would wreck an
engine, but everybody seems to have discovered that wasn't so as soon as they
needed to extend range.

USN numbers interesting. Thanks for posting.

Ah, found something, a note from a fellow who flew P-40Ns in the Pacific,
saying that he regularly flew combat missions of 800 miles, cruising to and
from the target area at 170IAS at 8,000ft., 30gph. This would get them over
the target with nearly empty 75g belly tanks, which they would jettison, do
their thing and head home, landing after about 5 hours in the air.


Chris Mark

Chris Mark wrote:

From: Guy Alcala

What was "normal" fuel consumption for the Zero?

I have a vague memory of reading 30-35gal./hr. somewhere, but don't hold me
to
it. The A6M2 had the Sakae 12 engine, which was only rated at 950 hp or so.

So by using the standard procedures outlined by Mr. Stickney, they were cutting
normal fuel consumption by about a third, which sounds right. There used to be
a belief in the long ago that low rpm and high manifold pressure would wreck an
engine, but everybody seems to have discovered that wasn't so as soon as they
needed to extend range.

My dad taught me to value overdrive gears and shift early for the same reason, many
years ago. I seem to get far better mileage than most people I talk to with the
same car do, and I don't drive around at LOL from Pasadena speeds. Come to think
of it, my first car, handed down from my Dad, was a '65 Chevy Impala SS with 3 on
the tree and an overdrive; it also had an MP gauge, but I confess I rarely paid any
attention to it. Barring the need for a rapid accel, I was in 3rd by 20 and 3rd
Over by 28-30, and the engine (283 V-8) was perfectly happy to do that. 240,000
miles and never had the head off, although it did leak oil pretty badly towards the
end of its 23 year career in my family. Compression was still within normal
limits, though.

USN numbers interesting. Thanks for posting.

Ah, found something, a note from a fellow who flew P-40Ns in the Pacific,
saying that he regularly flew combat missions of 800 miles, cruising to and
from the target area at 170IAS at 8,000ft., 30gph. This would get them over
the target with nearly empty 75g belly tanks, which they would jettison, do
their thing and head home, landing after about 5 hours in the air.

Yeah, that was the other advantage in the PTO, you could cruise most of the way to
the target at low to medium altitudes. While the air miles per gallon are better
at higher altitude, you aren't burning all the extra gas in the climb up to
altitude at high power settings. B-29s also benefitted from moderate outbound
cruise altitudes when bombing Japan. It was a lot easier on the engines, you didn't
need to be on O2 the whole mission, and you saved a bunch of fuel thatcould be
instead used to up the bombload.

That was generally the case in the Med too, but not in the ETO where you were
potentially in danger the moment you went feet dry over the continent, so you had
to cruise at high power settings at high altitude to avoid bounces. That's
probably the main reason why the P-38's Allisons worked well everywhere _but_ the
ETO.

Guy