Airscrew pitch control-1942? (4 Viewers)

[Writer]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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

 

[PStickney]

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

About Closterman - I suspect a mistranslation, although Pierre is a bit of an Unreliable Narrator.
To throw more fuel on the fire - Curtiss Electric Propeller controls had 2 modes - Automatic (Constant Speed) regulated by the Propeller Control Lever on the Throttle Quadrant, and Manual Mode, controlled by a 3-position Toggle Switch (Automatic (Constant Speed), Increase RPM, and Decrease RPM) where the Propeller operated in Fixed Pitch mode, with the pilot able to adjust the pitch using the (For lack of a better term) Propeller Mode Switch to set the propeller pitch as desired for that particular combination of Speed, Altitude and Manifold Pressure. Manual Mode, allowed a potential Runaway Propeller to be locked in pitch. Not optimum, but at least flyable.

 

[Engineman]

About Closterman - I suspect a mistranslation, although Pierre is a bit of an Unreliable Narrator.
To throw more fuel on the fire - Curtiss Electric Propeller controls had 2 modes - Automatic (Constant Speed) regulated by the Propeller Control Lever on the Throttle Quadrant, and Manual Mode, controlled by a 3-position Toggle Switch (Automatic (Constant Speed), Increase RPM, and Decrease RPM) where the Propeller operated in Fixed Pitch mode, with the pilot able to adjust the pitch using the (For lack of a better term) Propeller Mode Switch to set the propeller pitch as desired for that particular combination of Speed, Altitude and Manifold Pressure. Manual Mode, allowed a potential Runaway Propeller to be locked in pitch. Not optimum, but at least flyable.

The operating functions of the Curtiss Electric Propeller that you describe, are similar to the German VDM electric propeller in the Bf 109 late E to K, and others. The Electrical switching and functionality is similar. However, the VDM system also incorporated a prop pitch indicator "clock". The German word for automatic function was AUTOMATIK and for pilot controlled pitch adjustment by the HOTAS switch on the Throttle, it was HAND. Although the VDM system did include the pitch indicator "clock", its use was for the setting of specific pitch for Take-off and secondary HAND mode. The thumb operated propeller switch was inscribed DREHZAHL, meaning turning speed or rpm.

Eng

 

[MiTasol]

It may well that Pierre, as most if not all other pilots of the day, learnt on fixed pitch props, advanced to variable speed props and then considered constant speed props to be a new name for variable pitch props as this is not far off the reality. The only difference was in the control system, not the prop itself. VP props used a lever connected to a valve to vary the prop pitch. CS props use the same lever to vary the load on a spring and that spring operating on counterweights varies the prop pitch.

 

[Writer]

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

Hi Engineman.

Thank you for your erudite explanation but I'm still confused; if we take, say a Spitfire Mk IX, which we know had a constant speed airscrew, does this mean that there was also an airscrew pitch controller which, for example, would need to be used to put the airscrew into, say, fine pitch for takeoff and climb? and then moved, so that the aircraft cruised in coarse pitch? And would the Spitfire pilot then select a different pitch when entering combat?

I have read that Douglas Bader's first accident in a Spitfie Mk II was because he left the airscrew in coarse pitch when attempting a take off and the Spitfire accelearted too slowly. But if this accurate, (I dislike the word "truth"(!)), why was there any need for a constant speed airscrew? Couldn't the pilot simply control it all manually?

Finally, the Focke-Wulf 190 had the Kommandogerat, with one lever controlling engine revs, supercharger speed, throttle etc; Wouldn't this have given the pilot much greater time to look around and observe what he needed to see?

 

[Shortround6]

Finally, the Focke-Wulf 190 had the Kommandogerat, with one lever controlling engine revs, supercharger speed, throttle etc; Wouldn't this have given the pilot much greater time to look around and observe what he needed to see?

Yes, the last of the P-40s and some other allied aircraft shifted to a similar system to cut work load.

Thank you for your erudite explanation but I'm still confused; if we take, say a Spitfire Mk IX, which we know had a constant speed airscrew, does this mean that there was also an airscrew pitch controller which, for example, would need to be used to put the airscrew into, say, fine pitch for takeoff and climb? and then moved, so that the aircraft cruised in coarse pitch? And would the Spitfire pilot then select a different pitch when entering combat?

Unfortunately we often get confused between 2 pitch propellers, variable pitch propellers, adjustable pitch propellers (in flight vs adjustable on the ground) and constant speed.
At times the names changed for the same propeller. When there were no (or few) constant speed props 2 pitch props were often called variable pitch because they were not fixed pitch.

Constant speed is just that, constant speed. Pilot sets the propeller speed to what he wants, say 2600rpm for fast cruise and then sets throttle to get the air speed he wants. As the air changes as he climbs the pitch change mechanism will change the prop pitch to keep the 2600rpm. If the pilot does a few sharp turns and slows down the prop mechanism will adust to the pitch to finer to maintain the 2600rpm. In combat the pilot would select max rpm (3000) and the propeller would try to keep the engine turning 3000rpm by adjusting the prop to whatever pitch was needed to keep the engine at 3000rpm.