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Metatron_123
11-16-2009, 01:53 PM
In the 242 Squadron's mod pack is a mod that creates a propwash effect. It really changes the way you fly. If you get right on an enemy's six the propwash effect ruins your aim, and in extreme cases seems to have chopped one of my wings off(can anyone confirm this?)

Yet you see loads of gun camera clips where a plane is peppering the enemy right on its six.

Can someone explain the real life effects of propwash in combat and if this mod-effect is indeed over the top?

I have read that for example a damaged B-17 lost control after a P-51 flew past it, but can someone elaborate please..

TS_Sancho
11-16-2009, 02:14 PM
Someone will be along shortly to post a chart, I'm sure, but while I don't know about prop wash specifically, wake turbulence (of which prop wash would be a component) is a serious concern to aircraft.

Look at all the bomber pilot memoirs where they talk about all the work and concentration it took to hold close formation and how all it took was one aircraft sliding out of place to bounce the trailing aircraft into one another.

The FAA mandates that airliners maintain a horizontal separation of over 2 miles (its more specific based on weather, plane type etc. but forgive me for not sourcing the actual protocol)

Aircraft face a serious threat from wake turbulence, there have been a lot of accidents over the years attributed to it. I can only imagine that parking a couple hundred feet on the 6 of a 300 mph aircraft twisting and turning to save its life would be a bumpy ride indeed.

Metatron_123
11-16-2009, 02:49 PM
Hm, it's surprising not much whining has been going on concerning the lack of this feature for so long.

I wonder how pilots kept straight and level on someones six in spite of propwash...

TheGrunch
11-16-2009, 02:54 PM
Originally posted by Metatron_123:
I wonder how pilots kept straight and level on someones six in spite of propwash...
It's definitely damn hard with the mod. I hear ZloyPetrushko has submitted a version of his mod to Team Daidalos. He decided to omit the prop-wash, though, since he didn't consider it bug-free enough yet.

Metatron_123
11-16-2009, 03:04 PM
Yeah, I think the wing coming off part is a bit too much...

Gibbage1
11-16-2009, 04:36 PM
Having spent a LOT of time around running WWII aircraft on various TV shows for the History Channel, Military Channel, and Discovery, I can attest that they do throw up a lot of air behind them. I took this video myself on set (you can see the camera's in the cockpit windows attached with suction cups) and watch the puddle of water after the aircraft passes. Once the P-38 started to move, he's not much above idle.

Sorry for the bad sound quality.

http://www.youtube.com/watch?v=rIDWyKiWQ3Q

M_Gunz
11-16-2009, 04:59 PM
We have propwash from our own plane (make no mistake about that) and I've kind of wondered about from others since the start.
For it to work at all there must be some way in the code so kudos to ZloyPetrushko for bringing turbulence to game.

idonno
11-16-2009, 05:33 PM
In a real airplane, if you maintain your altitude through a tight enough 360 degree turn, you'll feel a bump when you fly through your own prowash.

M_Gunz
11-16-2009, 06:19 PM
Isn't that more than propwash? Like wingtip vortices which get stronger with increased induced drag?
Mostly I hear and read of all that as turbulence where propwash is your own affecting your plane.

Kettenhunde
11-16-2009, 06:28 PM
Sure you are not confusing the spiral slipstream of the propeller with wing vortexes? Both are present on any power producer and it is not hard to SWAG the effects.

I highly doubt any WWII aircraft would be ripping wings off another fighter sized airplane. Maybe a L-4 Grasshopper or a Storch...

doraemil
11-16-2009, 06:59 PM
BOB SOW is modeling propwash .. .

yeah need to overdub that p-38, doesn't do it justice

http://www.youtube.com/watch?v=PhORZrWOUfo

idonno
11-16-2009, 07:28 PM
Originally posted by Kettenhunde:
Sure you are not confusing the spiral slipstream of the propeller with wing vortexes?

The same sources that I've found which attribute the bump to wingtip vortices also correctly state the the vortices descend. That doesn't add up.

Kettenhunde
11-16-2009, 07:44 PM
The same sources that I've found which attribute the bump to wingtip vortices also correctly state the the vortices descend.


They do descend. You guys need the formula to calculate?

Just like the power, the rate of descent is based on the weight of the aircraft.

Gibbage1
11-16-2009, 07:54 PM
Ya. Tip vorticies descend. You can feel them at any airport with a local access road near the runway in the landing path. I would feel them all the time at John Wayne airport in Orange County California. Damn near knocks you off your feet, even though the aircraft that created it cleared you by a few hundred feet.

Daiichidoku
11-16-2009, 10:13 PM
your FSX angel in overalls is just fine, Gibbage

Gibbage1
11-16-2009, 10:42 PM
Originally posted by Daiichidoku:
your FSX angel in overalls is just fine, Gibbage

Eh? You mean my P-38? Im hoping to bring one of that quality to BoB if Oleg allows 3rd party add-on's, but thats a new thread, be sure!

M_Gunz
11-17-2009, 01:26 AM
Yup, the twirly part descends. And then what? A vacuum forms above as the air moves down and nothing is drawn
from above and the sides?

When a big plane lands at the airport, the air it passed through is fouled for a minute or more for small planes.
An unaware small plane pilot can find himself descending faster than he planned which is enough to ruin your day.

Metatron_123
11-17-2009, 01:47 AM
Originally posted by Kettenhunde:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The same sources that I've found which attribute the bump to wingtip vortices also correctly state the the vortices descend.


They do descend. You guys need the formula to calculate?

Just like the power, the rate of descent is based on the weight of the aircraft. </div></BLOCKQUOTE>

Hi. I'm lead to believe that you actually fly aircraft? Can you give me an idea of the implications of propwash in combat, in simple terms?

BillSwagger
11-17-2009, 03:07 AM
Well, something isn't right with the way it is now.

We had gone head to head from the start, and then my plane was brushed to the side as i got with in a couple hundred meters from the front of the other plane.

I know this is a bug, but it should be addressed and fixed along with what ever other changes are to be made.

I don't think its too extreme the way it is now, but something isn't right with how it is.


Bill

Kettenhunde
11-17-2009, 06:55 AM
Hi. I'm lead to believe that you actually fly aircraft? Can you give me an idea of the implications of propwash in combat, in simple terms?

Propeller spiral slipstream = bumpy ride... might mess up your aim if you are close enough.

Wing vortex or wake turbulence = Based on the weight of the aircraft and distance. A very heavy aircraft (airliner) wake turbulence can destroy a light plane (C172). Unless the weights are extreme though it is just a very bumpy ride. The strongest portion of the wave is twice the vertical velocity of the downdraft force found at the center of the wing.

To find the vortex strength = W or the down force velocity

Do you know how to find the AoA and induced AoA? Once again it is not hard but requires some number crunching. To shorten the explanation I left it out for now. Weight is factored through the induced angle of attack and velocity of the airplane.

Average relative wind the wing feels = AoA - Induced AoA

Average relative wind will be "a" for our purposes.


Velocity in KEAS * SIN (a/2) = W

100KEAS * SIN (9/2) = 7.85KEAS

2W = 15.69KEAS

2W is our new down force for the vortex. So you see it very simple to determine the down force velocity.


General rules to avoid wake turbulence:

1. Don't fly behind and below another airplane.

2. Place your mains after the nose wheel touches down of the airplane in front of you for landing

3. When taking off, rotate before the point the airplane in front of you rotated.

4. Rule of thumb, wake turbulence descends at ~500 fpm and moves with wind.

If an airliner is 500 feet above you descending to pattern altitude and 3NM away entering a downwind for the same runway you want to land on, if your plane is traveling 180Kts, you have a good chance of encountering his wake turbulence on a no wind day.

All the best,

Crumpp

Daiichidoku
11-17-2009, 10:13 AM
Originally posted by Metatron_123: Can you give me an idea of the implications of propwash in combat, in simple terms?

the spiral airflow of propwash will cause buffetting

im looking for it, but AFAIK it was in an ADFU test of the P38F vs spit IX that when the spit started (slowly) to get into a firing position on the 38 in a turn, it would hit the 38s propwash and make it considerably difficult to get a firing solution....


edited cuz Crumpp seems to have a hair up his a s s lately

Kettenhunde
11-17-2009, 10:35 AM
the broken airflow

It's Broken? OMG fix it!

TS_Sancho
11-17-2009, 10:55 AM
So I don't put my foot in my mouth in the future... I am incorrect in my statement that propwash would be a component of wake turbulence and while both make for bumpy air, wake turbulence is specifically wing vortex and prop slipstream is an entirely separate effect , correct?

Kettenhunde
11-17-2009, 11:52 AM
Wake turbulence is generally confined to the vortices formed by a wing creating lift.

Jet blast and Propeller slipstream are generally separate events with their own set of cautions. Slipstream will not effect an aircraft in the air very much beyond some bumps...light chop its called.

In the case of the P-38, it is twice the weight of the Spitfire and has the potential to put out some moderate chop to the Spitfire. Once again, this is a weight thing. In general, the higher the wing loading, the smoother the ride and less susceptible to turbulence the design.

That is why light sport aircraft have such low crosswind component and gust speeds. For example, A Zeke might experience heavy chop, a Spitfire moderate chop, and a Focke Wulf, light chop in a P38 Wake turbulence. I haven't done the math on that and I am not making a statement about any specific aircraft performance so Zeke fans, Spitfire fans, and Focke Wulf fans keep your pants on. Just an illustration of how weight effects gusting.

On a gusty day, the low wing loaded aircraft will be confined to a lower speed than a high wing loaded design.

How turbulence is defined:

http://www.bayareapilot.com/tu...ortingcriteriata.htm (http://www.bayareapilot.com/turbulencereportingcriteriata.htm)

Bremspropeller
11-17-2009, 12:40 PM
Simple exercise:

Go to the nearest airfield where they tow up gliders behind props.
Ask for a ride.
Tell the pilot youre an IL-2 ultra ace and that you're looking for the propwash-effect.
He's gonna fly you into it.

Some turbulence.

Exercise over.


Now what are you gonna learn:
Propwash only affects a tight area directly behind the leading aircraft.
It shakes you through a bit, but it's nothing to throw you off your feet.

Given the inertia of a 3+ ton aircraft, moving fast, it shouldn't do much more than throwing off you aim a bit.
Flying behind a B-17 at low speeds, though, will propably give you more of a shake (more engines, more slipstream + interference of propwash-tubes)

Gibbage1
11-17-2009, 01:09 PM
Im rather sure a 1600+ HP warbird will throw up a lot more propwash then a Cessna 172 dragging a glider.

Bremspropeller
11-17-2009, 01:39 PM
Depends what aircraft you're flying in relation http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

M_Gunz
11-17-2009, 01:56 PM
Just more reason to shoot deflection.

Kettenhunde
11-17-2009, 02:11 PM
Im rather sure a 1600+ HP warbird will throw up a lot more propwash then a Cessna 172 dragging a glider.


Pure Genius.

In fact, a little known offshoot of the Manhattan project, code named the Sesame Street Project developed a system that protected all USAAF fighters from the effects of German aircraft wake turbulence.

USAAF pilots were issued a code, "The letter of the Day" and to keep the Axis code breakers on their toes this was changed up occasionally with "The Number of the Day".

Late in war, a method of amplifying the USAAF wake turbulence was also developed. Any aircraft encountering, "Journey to Ernie" would be instantly destroyed.

Gibbage1
11-17-2009, 02:31 PM
You going to go off on clown pix, dead animals, and oil consumption rate of the P-47 again Ketten?

Kettenhunde
11-17-2009, 04:17 PM
Depends what aircraft you're flying in relation

You understand this part, Gibbage? Brems gave you a good example because the weight is relative to a certain point. The big heavies just generate so much down velocity and energy that they can still damage each other but they can also take much more than a lighter design.

The C172 weighs ~2300 at max and a Libelle 201B maxs out at 770lbs which is a 298% difference in weight. That is about like taking a P51D and moving it into a B25 wake turbulence.

All joking aside....I would like for you to understand it.

Kettenhunde
11-17-2009, 04:34 PM
edited cuz Crumpp seems to have a hair up his a s s lately

LOL

Bremspropeller
11-18-2009, 03:24 PM
The considerably higher wingload/ inertia of WW2-fighters will also help to flatten out any "bumpy road".

NuMcA_of_CS
11-18-2009, 09:45 PM
In a real airplane, if you maintain your altitude through a tight enough 360 degree turn, you'll feel a bump when you fly through your own prowash.
HAHAHA! would never have thought of that!! Experience beats all simulation! http://forums.ubi.com/images/smilies/metal.gif

Bremspropeller
11-19-2009, 12:20 PM
You also feel the bump when flying through your own wing-tip wakes.

Kettenhunde
11-19-2009, 07:02 PM
You also feel the bump when flying through your own wing-tip wakes.

It is not your prop wash, it is your wake vortex.

AndyJWest
11-19-2009, 07:17 PM
It is not your prop wash, it is your wake vortex.

At least part of the 'prop wash' will presumeably be wake vortex from the propeller blade tips, though I'd expect that to dissipate faster than the wingtip vortices. I'd have thought if you made a level turn, the wake vortex ought to be below you when you came back round to it. I'd also expect it to move outwards from the path of the turn, seeing as the aircraft would be banked. Is this correct?

idonno
11-19-2009, 07:25 PM
Originally posted by AndyJWest:
I'd have thought if you made a level turn, the wake vortex ought to be below you when you came back round to it.

That is exactly the point of my earlier post about the fact that the vortices sink.

M_Gunz
11-19-2009, 07:38 PM
How many people actually think that when you fly 360's that your path connects like a drawn circle or a
circle of road? If you make 2 360's does that mean each time you go through the same path? And your
height stays the same within say 1 meter?

Just wondering.

And again, when your wake pushes air down I suppose that no air is drawn in from above following it?
After all, the drawings and pictures don't show that do they?

idonno
11-19-2009, 08:01 PM
Originally posted by M_Gunz:
How many people actually think that when you fly 360's that your path connects like a drawn circle or a
circle of road? If you make 2 360's does that mean each time you go through the same path? And your
height stays the same within say 1 meter?

If you do it correctly, yes, you can cross your path again, and you wouldn't need to maintain your altitude within 1 meter. The area of disturbed air will certainly be a bit larger than that.


Originally posted by M_Gunz:
And again, when your wake pushes air down I suppose that no air is drawn in from above following it?
After all, the drawings and pictures don't show that do they?

The vortices don't descend at all that great of a rate, so they wouldn't generate that much of a downdraft. Also, when you fly through it, it doesn't feel like a downdraft, just disturbed air.

AndyJWest
11-19-2009, 08:09 PM
Of course you are unlikely to be able to fly consistant circles to that sort of accuracy, but if the vortex is descending, you shouldn't ever encounter it at all, which is what has been reported to happen.


...when your wake pushes air down I suppose that no air is drawn in from above following it?

Yes, obviously it must be. I would expect it to be moving more slowly and uniformly than the rapidly-rotating vortex though.

A practical way to check the descent rate of wingtip vortices: some birds - notably geese - fly in V formation to conserve energy by putting one wingtip into the opposite-rotation vortex of the bird in front. If the vortices are descending, the birds at the rear should be flying lower than those in front when in level flight: I'll see if I can find some evidence for this.

M_Gunz
11-19-2009, 10:02 PM
I've got a video on the making of "Father Goose" where the geese fly just off his ultralight's wingtips.
Sometimes the close ones are above and directly to the side or a bit ahead. Circulation affects air in
front and above the wing and I guess from watching those birds, even past the end.

All I'm saying is that without smoke to see you change heading by 360 and encounter disturbed air then
how do you tell what part you hit? In a tight turn close to stall what does it take to give you buffets?

idonno
11-19-2009, 10:47 PM
I'm not talking about turning so tight that you're approaching a stall.

I've done it several times. It is quite possible to maintain you altitude through a complete circle.

Bremspropeller
11-20-2009, 06:21 AM
Of course you are unlikely to be able to fly consistant circles to that sort of accuracy, but if the vortex is descending, you shouldn't ever encounter it at all, which is what has been reported to happen.


Well, I have experienced just that.
A330, two complete 360s over North-Pole with completely dead air.
We hit our own wakes once.

60m of wingspan at ~25 of bank will also give you some increased vertical target for the wakes.

Here's a pic of a Delta 763 at about similar speed and bank.
You can see, the wakes aren't that quick to sink:
http://www.airliners.net/photo...67-332-ER/1451255/L/ (http://www.airliners.net/photo/Delta-Air-Lines/Boeing-767-332-ER/1451255/L/)

Kettenhunde
11-20-2009, 06:58 AM
Of course you are unlikely to be able to fly consistant circles to that sort of accuracy, but if the vortex is descending, you shouldn't ever encounter it at all, which is what has been reported to happen.

Why don't you go fly some steep turns on a calm day and test that theory.


Every aircraft in flight generates a wake. Historically, when pilots encountered this wake in flight, the disturbance was attributed to "prop wash." It is known, however, that this disturbance is caused by a pair of counter rotating vortices trailing from the wing tips.

http://www.airweb.faa.gov/Regu...7/$FILE/AC90-23E.pdf (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/a9f7acc596ba2453862569e7006da9e7/$FILE/AC90-23E.pdf)

NuMcA_of_CS
11-20-2009, 07:23 AM
Now i am starting to confuse facts with fiction... damn!

Kettenhunde
11-20-2009, 07:42 AM
It is quite possible to maintain you altitude through a complete circle.


It is not possible, it is a requirement if you want to pass the practical....