F4U max speed only 200 knots

[Jimd0586]

Hey all. In level flight it seems I’m maxing around 200 knots. I did the rpm level pulldown with the mouse and still seem to max at 200 knots. Throttle open in level flight, landing gear up, supercharger fully forward… is there something I’m missing? Shouldn’t it max around 300 knots? Also flying a clean bird, no stores.

[Saxman]

Check your trim, beyond that there's definitely some odd behavior with the speed that's been reported several times. Even with injection on it's hit or miss whether the engine ever gets about 54in of manifold pressure.

[Jimd0586]

51 minutes ago, Saxman said:

Check your trim, beyond that there's definitely some odd behavior with the speed that's been reported several times. Even with injection on it's hit or miss whether the engine ever gets about 54in of manifold pressure.

Thank you. I’ll check that. I’m also wondering if the cowl flaps may have something to do with it as well.

[gabuzomeu]

Cowl flaps create major drag indeed and must be almost closed to go fast.

Also, mention altitude where you measure speed (Indicated? ctrl-y will display, when repeated, TAS)

[Gunfreak]

At 22000 feet. High blower, all hatches and toilet seats closed.  2700rpm, 59MP. "Water activated" if that even does anything. I get 370mph once corrected to true airspeed and converted to MPH. 22000 should be the altitude the Corsair reaches 410mph. So I'm missing 40mph.

[Ghostrider 147]

6 hours ago, Jimd0586 said:

Hey all. In level flight it seems I’m maxing around 200 knots. I did the rpm level pulldown with the mouse and still seem to max at 200 knots. Throttle open in level flight, landing gear up, supercharger fully forward… is there something I’m missing? Shouldn’t it max around 300 knots? Also flying a clean bird, no stores.

Don't pull the RPM lever down with the mouse, that's a bug, the Corsair's engine is rated for 2700 RPM maximum. Also be aware that at altitude the air density is less and the IAS will read lower values the higher you go, use the info bar at the bottom of your screen to read the True Air Speed (TAS) value (Ctrl+Y I believe).

To achieve maximum speed at sea level use full RPM (2700 RPM) and full throttle (manifold pressure will be around 58-59 inHg I believe). Close your oil cooler and intercooler flaps for minimum drag, cowl flaps can also be closed or keep them open about 1/4th to 1/3rd to keep the engine itself from overheating. Use your rudder pedals to stay coordinated (keep the ''ball'' in the middle, use the slip indicator on the gun sight for instance). At altitude, use the supercharger (blower) to maintain the maximum manifold pressure. Remember that in the Corsair max blower means pulling the lever back, not fully forward. Open the intercooler flap about halfway to keep the supercharger cool.

Using this I'm able to reach the F4U-1D's official top speeds as in the official charts. It's a lot to keep in mind but after some practice all these actions become second nature  Good luck!

Edited July 7 by Ghostrider 147
Typo

[Jimd0586]

Thanks all for the help! Lots to remember!

[Saxman]

7 hours ago, Ghostrider 147 said:

Don't pull the RPM lever down with the mouse, that's a bug, the Corsair's engine is rated for 2700 RPM maximum. Also be aware that at altitude the air density is less and the IAS will read lower values the higher you go, use the info bar at the bottom of your screen to read the True Air Speed (TAS) value (Ctrl+Y I believe).

To achieve maximum speed at sea level use full RPM (2700 RPM) and full throttle (manifold pressure will be around 58-59 inHg I believe). Close your oil cooler and intercooler flaps for minimum drag, cowl flaps can also be closed or keep them open about 1/4th to 1/3rd to keep the engine itself from overheating. Use your rudder pedals to stay coordinated (keep the ''ball'' in the middle, use the slip indicator on the gun sight for instance). At altitude, use the supercharger (blower) to maintain the maximum manifold pressure. Remember that in the Corsair max blower means pulling the lever back, not fully forward. Open the intercooler flap about halfway to keep the supercharger cool.

Using this I'm able to reach the F4U-1D's official top speeds as in the official charts. It's a lot to keep in mind but after some practice all these actions become second nature  Good luck!

The odd thing is I can (almost) never get full MAP with injection on. The needle almost never gets above 54in. And when I can I can never figure out what combinations of settings get it there. It seems sometimes going to Auto Rich boots it up, sometimes going into high blower even below critical altitude, sometimes NO blower.

[gabuzomeu]

The real aircraft manual states Auto Lean shall be used with water injection.

And , I can't figure out the actual role of the "water injection" button

[gabuzomeu]

Just tried and got 346kts TAS @ 21 500', that's 398mph. (screenshot before reaching max)

Question: which max speed table do you all refer to?

low fuel (<50%), auto lean, 2 700 rpm. 63 in Hg pressure. (Still no clue about water injection button)

[Saxman]

2 hours ago, gabuzomeu said:

The real aircraft manual states Auto Lean shall be used with water injection.

And , I can't figure out the actual role of the "water injection" button

I'm aware of this. However there's been some reports that the engine may be modeled as the -8 version of the engine, rather than the 8W (water injected). So I was basically trying whatever to see what stuck.

The water injection button turns the water injection system on. This is one of the questions about the current engine model because injection in the Corsair was automatic based on throttle position, not a separate control.

2 hours ago, gabuzomeu said:

Just tried and got 346kts TAS @ 21 500', that's 398mph. (screenshot before reaching max)

Which is about 10mph too slow.

2 hours ago, gabuzomeu said:

Question: which max speed table do you all refer to?

At critical altitude the F4U-1D should be about 410mph TAS. There's not a speed table for the 1D that I'm aware of, all of the tests we have data for are for seem to be from F4U-1As. The 1D loses an average of 10mph over the 1A because of drag for the knuckle pylons, so it can be estimated from there.

Edited July 7 by Saxman

[Ala13_ManOWar]

2 hours ago, gabuzomeu said:

Just tried and got 346kts TAS @ 21 500', that's 398mph. (screenshot before reaching max)

Question: which max speed table do you all refer to?

low fuel (<50%), auto lean, 2 700 rpm. 63 in Hg pressure. (Still no clue about water injection button)

I don't see it in the screenshot, but, are you flying on an ISA conditions atmosphere? otherwise you'll never get the listed TAS.

Remember, all your tests should be performed on international standard atmospheric conditions (ISA), meaning T=15º C, Pressure = 1013'25mb , otherwise numbers won't ever match.

Edited July 7 by Ala13_ManOWar

[gabuzomeu]

Yes, 15° at sea level and 29.92 in Hg.

I guess we are really not that far in termes of speed.

I have the feeling acceleration is sluggish, but I have no reference or doc , just an impression.