The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

little, then suddenly the jolting stopped as the plane became airborne.
Retracting the undercarriage, he waited a few moments whilst his speed
increased, then eased back the control column and began to climb away.
Looking either side of him, he watched the position of the others and then
they began to tighten up for the climb.
They met cloud over Kent, but as they approached London the sky cleared,
just as the met officer had predicted. Everyone began scanning the sky, but
nothing could be seen – yet. The engine in front of him throbbed
rhythmically. It was noisy in any fighter, but with his headphones strapped
close to his ears it became such a constant background thrum that he might
as well have been flying in silence; and the silence in his headset only
added to the tension he felt as he waited for the moment the British fighters
would be spotted.
Ulrich continued searching the sky behind, in front, either side, below,
but especially above. Suddenly a voice full of static crackled in his ear,
‘Raven calling! Raven calling! Eleven o’clock high! Eleven o’clock high.
Condensation trails, same course.’ Ulrich looked up and saw them now,
about 3,000 feet above, to their left, the vivid white contrails clear against
the deep blue. The fighting had got higher in recent weeks. The Gruppe
were already at 32,000 feet, which meant the Spitfires were now at 35,000,
an incredible height. It was hard flying at those heights. The 109 did not
like it and the pilots had to constantly change the propeller pitch and throttle
to improve performance: with a fine pitch, they could increase the RPM and
get more pressure from the engine’s supercharger, but by then switching to
coarse pitch they could make up some speed, which was essential if they
were to keep up with the rest of the formation.
But there was something up with Yellow 2. Ulrich was struggling to
change pitch. Most probably condensation had begun to collect in the
grease of the pitch-changing gear during the cold nights of the past week,
and now, at 32,000 feet, it had frozen, which had affected the pitch control.
For a moment, Ulrich thought about turning back but then dismissed the
idea, opting instead to keep the pitch fine and run the engine at high revs
and rely on the supercharger to help maintain speed. It meant the engine
would be running at a level higher than the recommended RPM, but that
happened all the time in combat. In any case, having made his decision to
fly on, he did not have any other choice.