Airscrew pitch control-1942? (1 Viewer)

Writer · Wednesday at 5:57 AM

I am just re-reading Pierre Closterman's "The Big Show". Very early on, he talks about flying a Spitfire Mk IX. Twice he mentions adjusting the pitch of the airscrew.
I believe that by 1940, Spitfires and Hurricanes were fitted with contact speed airscrews, requiring no manual pitch change so is this a mistake of Closterman's or is there more to this?

Michael Hope · Wednesday at 12:45 PM

Attached is an image of a constant speed propeller and the plumbing to the governor which controls the propeller RPM. The governor is how the RPM is set which is controlled by the pilot. The pilot sets a high RPM for takeoff, and the lower RPM for cruise. The sample in the image would be a Hamilton Standard counterweight propeller and governor. Rotol used a similar system.

Writer · Wednesday at 3:23 PM

Michael Hope said:
Attached is an image of a constant speed propeller and the plumbing to the governor which controls the propeller RPM. The governor is how the RPM is set which is controlled by the pilot. The pilot sets a high RPM for takeoff, and the lower RPM for cruise. The sample in the image would be a Hamilton Standard counterweight propeller and governor. Rotol used a similar system.

Thank you. Very interesting. I thought that a constant speed airscrew meant that a pilot did not need to select the pitch at all, the airscrew doing all the work, in choosing what pitch was best for what throttle setting. So-airscrew would be in fine pitch for take off, coarse for cruise but as soon as the pilot went into combat, he gave the engine full throttle and the airscrew adopted the correct pitch automatically...

Engineman · Wednesday at 4:12 PM

Hi,
You are misinterpreting the term. In general use, the term "Constant speed airscrew" followed-on from the earlier "adjustable-pitch", "two-pitch", and "variable-pitch" types that
developed in the 1920's and 1930's. The Constant speed airscrew is normally one that has a variable pitch function coupled to a speed sensitive governor that allows selectable
rpm of the aircraft engine and propeller by selection via a lever. This is quite a complicated subject as it is possible for the specific functionality of the system used to vary
somewhat in the manner of operation. Additionally, no aircraft propeller system is ever totally "Constant-Speed", there are always regions of the engine-propeller operation where the speed varies, by design. Notwithstanding that, there have been engine-propeller systems that function as single-lever power controls, but they still achieve variable engine-propeller rpm and automatic variable-pitch control.

Eng

Bretoal2 · 2025-12-04T04:25:51-0500

See the "Spitfire IX XI XVI manual", here (post #1) :

Spitfire Manuals

Spitfire IX, XI, XVI, Here's one for you lancaster kicks *** Enjoy Micdrow

ww2aircraft.net

Part V : 33 = Throttle lever - 35 = Propeller speed control

Lever 35 is obviously a "pitch control" !

Engineman · 2025-12-04T05:36:57-0500

Bretoal2 said:
See the "Spitfire IX XI XVI manual", here (post #1) :

Spitfire Manuals

Spitfire IX, XI, XVI, Here's one for you lancaster kicks *** Enjoy Micdrow

ww2aircraft.net

Part V : 33 = Throttle lever - 35 = Propeller speed control

Lever 35 is obviously a "pitch control" !

See also pages 12 and 13 for the Throttle and Propeller control. In para 20(i) it specifically states "the speed control lever" "varies the governed rpm". There is no mention of Pitch. However, the Constant speed governor does control rpm by changing the blade pitch to suit.
You will also note, the AUTOMATIC function in later aircraft, where the Overide function of the lever links the throttle position to the constant speed unit, or works as the speed control lever when not linked in the Overide setting.

Eng

Engineman · 2025-12-04T05:58:42-0500

Interestingly, the linked "Automatic" throttle/propeller speed control function used by R-R on some later engines/aircraft, was an adoption of the German VDM AUTOMATIK system used on the Bf 109 from 1940, in function though, not in the actual mechanical arrangement.

Eng

Bretoal2 · 2025-12-04T06:45:32-0500

Engineman said:
See also pages 12 and 13 for the Throttle and Propeller control. In para 20(i) it specifically states "the speed control lever" "varies the governed rpm". There is no mention of Pitch. However, the Constant speed governor does control rpm by changing the blade pitch to suit.
You will also note, the AUTOMATIC function in later aircraft, where the Overide function of the lever links the throttle position to the constant speed unit, or works as the speed control lever when not linked in the Overide setting.

Eng

Yes, of course, the booklet doesn't write "pitch control." But what can a "propeller speed control" do besides varying the propeller pitch?

With the same throttle opening : reducing propeller speed = more pitch, increasing propeller speed = less pitch.

Therefore, the pilot must use levers 33 and 35 simultaneously to maintain the engine at optimal efficiency depending on the task (climb - cruise level - full speed level - dive).

With one eye on the tachometer, another on the manifold pressure, and a third one on the enemy.

Engineman · 2025-12-04T07:07:18-0500

Bretoal2 said:
Yes, of course, the booklet doesn't write "pitch control." But what can a "propeller speed control" do besides varying the propeller pitch?

With the same throttle opening : reducing propeller speed = more pitch, increasing propeller speed = less pitch.

Therefore, the pilot must use levers 33 and 35 simultaneously to maintain the engine at optimal efficiency depending on the task (climb - cruise level - full speed level - dive).

With one eye on the tachometer, another on the manifold pressure, and a third one on the enemy.

No, your description is inaccurate. The control system function is to control rpm, of the propeller and engine. The CSU senses only rpm, it has no feedback from propeller pitch.
Of course, the propeller pitch is changed by the CSU response to underspeed or overspeed, but the function of the CSU is as an rpm controller.
With the Merlin engines described, the pilot does not have to balance anything, with the early speed control lever, he simply selects the desired rpm and opens the throttle to the desired Boost. With the later Linked control, with the Overide lever selected to AUTOMATIC the Throttle lever position controls both rpm and Boost in the fixed relationship shown in the table on p.13.

Cheers

Eng

Bretoal2 · 2025-12-04T07:56:58-0500

Engineman said:
No, your description is inaccurate. The control system function is to control rpm, of the propeller and engine. The CSU senses only rpm, it has no feedback from propeller pitch.
Of course, the propeller pitch is changed by the CSU response to underspeed or overspeed, but the function of the CSU is as an rpm controller.
With the Merlin engines described, the pilot does not have to balance anything, with the early speed control lever, he simply selects the desired rpm and opens the throttle to the desired Boost. With the later Linked control, with the Overide lever selected to AUTOMATIC the Throttle position controls both rpm and Boost in the fixed relationship shown in the table on p.13.

Cheers

Eng

I'm not talking about some kind of CSU or British or American Kommandogeratt, but rather the instruments and levers actually present in a Spitfire Mk IX. They explain Clostermann's statement, as reported in post #1 : "Twice he mentions adjusting the pitch of the airscrew."

These levers act on the carburetor throttle and the propeller control. The latter can do nothing other than modify the pitch.

Let's therefore admit that "adjusting the pitch" is a simplification, simply describing the effect of the pilot's actions on this lever: changing the pitch.

Engineman · 2025-12-04T08:36:12-0500

Bretoal2 said:
I'm not talking about some kind of CSU or British or American Kommandogeratt, but rather the instruments and levers actually present in a Spitfire Mk IX. They explain Clostermann's statement, as reported in post #1 : "Twice he mentions adjusting the pitch of the airscrew."

These levers act on the carburetor throttle and the propeller control. The latter can do nothing other than modify the pitch.

Let's therefore admit that "adjusting the pitch" is a simplification, simply describing the effect of the pilot's actions on this lever: changing the pitch.

Hi,

The correct detail of how these systems function is important, witness the incorrect statement apparently quoted, or was it a miss-translation? The only Spitfires with selectable "Pitch
lever" were those with variable pitch propellers but without a CSU. Maybe he was confused and quoting his older memory?
In truth, the CSU controls rpm and that is its function. The pilot operating this system should only think in terms of engine rpm, he has no indication of propeller blade pitch.

Eng

Engineman · 2025-12-04T08:47:43-0500

Writer said:
I am just re-reading Pierre Closterman's "The Big Show". Very early on, he talks about flying a Spitfire Mk IX. Twice he mentions adjusting the pitch of the airscrew.
I believe that by 1940, Spitfires and Hurricanes were fitted with contact speed airscrews, requiring no manual pitch change so is this a mistake of Closterman's or is there more to this?

Hi, you may see from the posts that there is more to this. The function of engine control did change greatly with the introduction of Constant speed control.
I hope you can see the difference between the systems.

Eng

Airscrew pitch control-1942? (1 Viewer)

More options

Writer

Airman

Michael Hope

Airman 1st Class

Attachments

Writer

Airman

Engineman

Staff Sergeant

Bretoal2

Senior Airman

Spitfire Manuals

Engineman

Staff Sergeant

Spitfire Manuals

Engineman

Staff Sergeant

Bretoal2

Senior Airman

Engineman

Staff Sergeant

Bretoal2

Senior Airman

Engineman

Staff Sergeant

Engineman

Staff Sergeant

Users who are viewing this thread

Similar threads