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View Full Version : How much drag do the radiator flaps actually make?



Moustacheo
08-21-2005, 06:29 AM
I've been wondering how much drag the radiator flaps actually create, since often I can open them fully with almost no difference to my speed. I'm not saying that the drag isn't modelled, but I'm just wondering if the small increase in drag is really that bad compared to the cooling you get with a fully open radiator.

Also, does opening the radiator on the I-16 create any drag at all? It doesn't have any radiator flaps on the side of the plane, only slots that open directly on the front of the engine. Is the only drawback for opening the radiator on the I-16 exposing the engine?

VW-IceFire
08-21-2005, 07:53 AM
Planes like the I-16 and FW190 still create radiator drag with their rads open. I don't understand exactly how but Oleg explained it to us...the air still slows going in and out of the engine so I guess that means drag.

Ask an aeronautical engineer to properly explain I guess.

Rads can take 20-30kph or more off your top speed. Wise to manage your radiators.

I usually open or halfway open most of the time and close for dives and such.

Taylortony
08-21-2005, 08:58 AM
One exception to the rule was the P51, the shape of the ducting on that actually produced thrust similar to a jet engine.

3.JG51_BigBear
08-21-2005, 09:32 AM
Like Icefire said the radiator systems on planes like the I16, La5/7, FW190, and others have complex air ducts running around inside the cowling. As air runs through these ducts it creates a noticeable amount of drag. The greatest difference in speed can be seen in the Bf109. I've read pilot's acounts in which openning the radiator fully was described as being similar to "putting on the brakes" and along with intentionally spinning out was a great way to make an opponent overshoot, much safer too I'd think.

I never fly with the radiator fully open unless I'm in a very steep climb that's going to last for a significant amount of time or the engine has overheated/will soon overheat. On most planes you can fly for quite a while at around 95% throttle without needing to open the radiator. If you manage the radiator you can keep your speed higher over a longer period of time.

LStarosta
08-21-2005, 10:48 AM
Originally posted by Taylortony:
One exception to the rule was the P51, the shape of the ducting on that actually produced thrust similar to a jet engine.


Not completely true. The Meredith effect created some thrust, but not enough to completely offset the drag created by the radiator being there in the first place.

In other words there was no net gain in thrust, and there was still a net gain in drag.

Moustacheo
08-21-2005, 12:03 PM
Thanks for the replies. Does anyone also know if the game has modelled that opening the radiator makes it more vulnerable to bullets and flak?

1.JaVA_Razer
08-21-2005, 12:41 PM
YES

the IL2's oiler cooler is supervulnerable with rad open but with rad closed it's very well protected.

Open rad + bullet inside rad = engine dead in a matter of minuts

FritzGryphon
08-21-2005, 03:22 PM
For reference, a full open radiator on the Bf-109G2 causes a reduction in top speed of 50km/h at sea level, or about 10%.

Other planes probably similar.

Hristo_
08-21-2005, 03:29 PM
AFAIK, D-9 radiator also used Meredith effect.

ClnlSandersLite
08-21-2005, 10:38 PM
Whenever you set out to learn a new plane, there's plenty of tests you need to do. How top speed is effected by various things, like radiator, flaps, etc is just one of them. You also need to figure out how long it can stay up on a couple of different engine settings, how much trigger time it has, where it has nasty flight charasteristics, best landing speed, how flaps effect yake off, what surfaces are trimmable, etc.

Since there is no documentation on ANY of this for any of the planes, you just have to spend a couple of hours in the ride figuring this **** out. No real way around it.

If you're doing a one off kind of thing and have no intention of spending too much time in a plane, just use some common sense and wisdom aquired from similiar air frames.

womenfly
08-22-2005, 07:50 AM
Originally posted by ClnlSandersLite:
Whenever you set out to learn a new plane, there's plenty of tests you need to do. How top speed is effected by various things, like radiator, flaps, etc is just one of them. You also need to figure out how long it can stay up on a couple of different engine settings, how much trigger time it has, where it has nasty flight charasteristics, best landing speed, how flaps effect yake off, what surfaces are trimmable, etc.

Since there is no documentation on ANY of this for any of the planes, you just have to spend a couple of hours in the ride figuring this **** out. No real way around it.

If you're doing a one off kind of thing and have no intention of spending too much time in a plane, just use some common sense and wisdom aquired from similiar air frames.

Very interesting statement. How about everyone start posting a best settings document for the plane you know the best in this sim (not the actual real aircraft spec's but the sim planes spec's)? Flight speed, nasty habits, dive speeds, landing speeds, etc..

Just a thought ... http://forums.ubi.com/images/smilies/heart.gif

ClnlSandersLite
08-22-2005, 12:12 PM
Originally posted by womenfly:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ClnlSandersLite:
Whenever you set out to learn a new plane, there's plenty of tests you need to do. How top speed is effected by various things, like radiator, flaps, etc is just one of them. You also need to figure out how long it can stay up on a couple of different engine settings, how much trigger time it has, where it has nasty flight charasteristics, best landing speed, how flaps effect yake off, what surfaces are trimmable, etc.

Since there is no documentation on ANY of this for any of the planes, you just have to spend a couple of hours in the ride figuring this **** out. No real way around it.

If you're doing a one off kind of thing and have no intention of spending too much time in a plane, just use some common sense and wisdom aquired from similiar air frames.

Very interesting statement. How about everyone start posting a best settings document for the plane you know the best in this sim (not the actual real aircraft spec's but the sim planes spec's)? Flight speed, nasty habits, dive speeds, landing speeds, etc..

Just a thought ... http://forums.ubi.com/images/smilies/heart.gif </div></BLOCKQUOTE>

Maybe a section for the community manual at air warfare?

Dash_C.
08-22-2005, 01:24 PM
Originally posted by ClnlSandersLite:
Whenever you set out to learn a new plane, there's plenty of tests you need to do. How top speed is effected by various things, like radiator, flaps, etc is just one of them. You also need to figure out how long it can stay up on a couple of different engine settings, how much trigger time it has, where it has nasty flight charasteristics, best landing speed, how flaps effect yake off, what surfaces are trimmable, etc.

Since there is no documentation on ANY of this for any of the planes, you just have to spend a couple of hours in the ride figuring this **** out. No real way around it.

If you're doing a one off kind of thing and have no intention of spending too much time in a plane, just use some common sense and wisdom aquired from similiar air frames.

Interesting you should mention this. Before yesterday, I hadn't given much thought to supercharger stages and radiator settings in all the years I've had IL2. Then, I decided to take an La-5 out for a spin just to play with these things. It's interesting how certain configurations affect performace in different ways. I've realized that you really have to get to know the plane in order to get every last bit of performance out of it.

And to womenfly: I agree, some kind of database or documentation is needed to summarize all of the optimum configurations for each aircraft.