Throttle and Boost lever interconnect. DCS manual is incorrect.

[kermitlefrog]

DCS is awesome and I love the P47D however there appears to be a problem. The training videos and all subsequent videos I have seen specify linking the throttle and boost levers all the time. Even for take-off. The manual advises this is only OK in exceptional circumstances and never below 7000 ft. See here: https://www.youtube.com/watch?v=HHtypRJuNKY&t=31s

As mentioned in the video DCS may not have modelled this correctly and the 300HP loss may not occur in the module but I still feel the correct procedures should be specified.

[grafspee]

If you want 52" you have to use turbo for this. This was already discussed and P-47 manual say it clearly that for 52" you need use turbo. Full throttle should give around 45" .

DCS got this modeled correctly.

Edited October 16, 2021 by grafspee

[saburo_cz]

1 hour ago, kermitlefrog said:

never below 7000 ft

This was relevant to only when 91 octane fuel was used. This fuel was used for training units in the USA during WWII.

When 100 otane fuel was used, all combat units (this fuel is modeld in the DCS W for Allied planes), interconect could use from ground up to critical altitude.

For take-off in this case, pilot should use "take-off stop", it was throttle stop which prevent thottle lever from going above 52inHg MP. 

[grafspee]

Only concern with 100 octane fuel is carb air temp, at very hot day use turb during take off would exceed carb air temp limit so, sometimes you take off w/o turbo.

But no altitude limits for turbo anymore with 100 octane fuel.

[kermitlefrog]

Interesting. Thank you. Is there a time limit on 52" or is it dependent on temperatures?

Also, if you want cruise at 42" would it not be better to have the throttle fully open (and thus reduce throttling losses) and only then use boost (if required) to bring it up to 42"?

Edited October 16, 2021 by kermitlefrog

[grafspee]

13 minutes ago, kermitlefrog said:

Interesting. Thank you. Is there a time limit on 52" or is it dependent on temperatures?

Also, if you want cruise at 42" would it not be better to have the throttle fully open (and thus reduce throttling losses) and only then use boost (if required) to bring it up to 42"?

 

Ofc it is better i always fly that way. Throttle full  then  i add boost through the turbo. This way you get lower carb air temp at same MAP and this equals more power  

But at sea level you need both throttle and booster lever full on to get 52" 

Edited October 16, 2021 by grafspee

[kermitlefrog]

1 minute ago, grafspee said:

Ofc it is better i always fly that way. Throttle full  then  i add boost through the turbo. This way you get lower carb air temp at same MAP and this equals more power  

So the tutorial is wrong to say use the interconnect at all times.

[grafspee]

10 minutes ago, kermitlefrog said:

So the tutorial is wrong to say use the interconnect at all times.

If it says like that then yes, for example at hot day you can't interconnect throttle for take off carb air temp is limiting factor.

Second case, you don't need 52" for every take off, you can take off w/o turbo

Third case, no turbo for engine/accessories test as well

Edited October 16, 2021 by grafspee

[some1]

Basically whenever you're using a turbo without opening the throttle fully, you're wasting power (and fuel). You're boosting and choking the engine at the same time.  You're limiting the efficiency of the supercharger, which is mechanically linked to the engine and costs you a fixed amount of horsepower. The turbo has to work harder which also increases the back pressure on the engine. Neither is good.

The only reason for the interconnect is the ease of operation and to prevent the pilot from pulling back the throttle while keeping turbo lever forward. 

 

Edited October 16, 2021 by some1

[saburo_cz]

27 minutes ago, kermitlefrog said:

Is there a time limit on 52" or is it dependent on temperatures?

Yes it is. You may use 52inHg/2700RPM for 15 minutes, according to manual.

But only if you keep your engine in limits, temperature and pressure. This must be obeyed in all situations, even when engine is idling. You can`t go above limits.

 

btw. 52inHg is attainable at very low altitude without turbo, but only if you fly fast, really fast - 500kph, RAM effect will help you.

[kermitlefrog]

Basically whenever you're using a turbo without opening the throttle fully, you're wasting power (and fuel). You're boosting and choking the engine at the same time.  You're limiting the efficiency of the supercharger, which is mechanically linked to the engine and costs you a fixed amount of horsepower. The turbo has to work harder which also increases the back pressure on the engine. Neither is good.
The only reason for the interconnect is the ease of operation and to prevent the pilot from pulling back the throttle while keeping turbo lever forward. 
 

This is exactly how I understand it. Very well explained in Greg's video.

Sent from my LLD-L31 using Tapatalk

[grafspee]

3 hours ago, saburo_cz said:

Yes it is. You may use 52inHg/2700RPM for 15 minutes, according to manual.

But only if you keep your engine in limits, temperature and pressure. This must be obeyed in all situations, even when engine is idling. You can`t go above limits.

 

btw. 52inHg is attainable at very low altitude without turbo, but only if you fly fast, really fast - 500kph, RAM effect will help you.

I think i got like 56" w/o turbo in high speed dive

[Diesel_Thunder]

23 hours ago, kermitlefrog said:

Interesting. Thank you. Is there a time limit on 52" or is it dependent on temperatures?

Also, if you want cruise at 42" would it not be better to have the throttle fully open (and thus reduce throttling losses) and only then use boost (if required) to bring it up to 42"?

 

This should help for your first question:

And yes, you use full throttle and supplement as needed with the turbo. Big thing to pay attention to as well is not ever allowing the engine to be windmilled so you aren’t damaging the crankshaft bearings.

[grafspee]

@kermitlefrog What i found beside engine time limitations, the oil temp is very important, always remember when switching in to higher power to open oil cooler, i often open it almost max. I noticed that oil temp likes to hit 100C very easy.