Peter Stickney wrote:

In article ,
Orval Fairbairn writes:
In article ,
ost (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?



Chris Mark


They achieved thos numbers by cutting back to 20%-30% power and
aggressive leaning. Lindbergh taught the same concepts to USAAF P-38
pilots -- this technique is part of what enabled the Yamamoto shootdown.
The P-38s were operating way outside their expected normal combat radius.

Y'know, that's been mentioned any number of times about Lindberg's
trip to the Pacific. But I have some doubts about it.
The Carbs used on the later model P-38s were Bendix-Stromberg PD 12
pressure carbs. IIRC, These didn't have manual adjustment - you had
settings of "Full Rich", Auto-Rich", "Auto-Lean", and "Idle Cutoff".
you couldn't manually lean the engines.

The secret to a low fuel burn is low RPM/High BMEP. To get this, you
need to crank the prop to the desired cruise RPM (Usually Full Decrease or
thereabouts, set the throttle to the maximum setting that maintains
that RPM, and pull the mixture back to Auto-Lean. If you've chosen
the proper cruise altitude, you'll be chugging along at the minumum
drag IAS (Speed for best climb), and what determines your endurance
will be whether the relief tube's plugged.
I suspect that that's wht Lindy really taught them.

Exactly right. They'd been cruising in auto-rich, low MP/high rpm. He told them to
put it in auto-lean, pull the prop back to 1,800 rpm and then advance the throttle
until they got 180mph IAS (they'd been cruising at higher speeds).

It's not a great condition to be in if you're bounced, however - you
can't just shove teh throttle forward & go. A Big recip can be
remarkably delicate at times, and just shoving the throttle forward at
low revs with a lean mixture is asking it to come apart. To spool
things up, you've got to do the hand-jive, shoving teh mixture to Full
Rich first, the prop to Full Increase, and then you can bring up the
power with the throttle. I can see somebody who's concerned about
being bounced keeping the mixture up in the AUto-Rich range and just
fiddling with the revs (Prop) and Manifold Pressure (Throttle).

The advantage of the late-war Pacific was that most of the time you were flying over
uninhabited areas or the sea, so really didn't need to worry about getting bounced
except in the vicinity of airfields. The Japanese lack of fuel also played a part.
The details are in Lindbergh's wartime journal, but IIRR the increased radii guarantees
he made to Kenney, or maybe it was Whitehead, included going to auto rich and (IIRC)
combat cruise speed in the combat zone, which I think he defined as 100 miles both in
and out, plus combat allowance, etc. The crews didn't necessarily believe him the
first couple of missions, but when they noticed he was returning to base with 100-200
gallons more fuel than they while flying the same missions, they paid attention.

Guy