On the topic of Thunderbolts

[Bremspropeller]

3 minutes ago, Legioneod said:

First hand accounts are a good way to see how an aircraft performed in combat vs what the numbers say it could do.

That also has to be seen in relative terms, because we have distinct survivor bias telling the story. We don't get to hear from the people that couldn't handle the airplane.

Hence every airplane somebody writes an ace-memoir about is the greatest thing since sliced bread.

 

I'd agree with you that it does give a good background on what the airplane could do with a good (and lucky) pilot. But it's not applicable across the board.

[ZachariasX]

3 minutes ago, Legioneod said:

First hand accounts are a good way to see how an aircraft performed in combat vs what the numbers say it could do.

It much rather shows what these persons right there and then could make of it.

 

I think hard data, as well as eyewitnes report hold metit and both are required to get a picture if the actual situation. Even though eyewitness do not always tell „the truth“, they have different motives and hence a different vantage point. Them giving a different pictures does not really make them liars. Buteverything adds up to a bigger puzzle. And by listening to first hand accounts while knowing hard numbers, one might also learn a lot about the person telling his or her story.

[Legioneod]

1 minute ago, Bremspropeller said:

That also has to be seen in relative terms, because we have distinct survivor bias telling the story. We don't get to hear from the people that couldn't handle the airplane.

Hence every airplane somebody writes an ace-memoir about is the greatest thing since sliced bread.

 

I'd agree with you that it does give a good background on what the airplane could do with a good (and lucky) pilot. But it's not applicable across the board.

Clearly. I agree.

 

All I'm saying is that we really need both to get a complete picture of the situation.

[Bremspropeller]

3 minutes ago, novicebutdeadly said:

Not only is there compressability at speed, but also aileron reversal,

I vaguely remember reading that Spitfires aileron reversal speed was below that of it's critical mach number (until the Mark XXI which had a stiffened wing).

I wonder if when compressability is modeled if aileron reversal will also

be modeled??

 

Please excuse my smartassery, but I've been biting my nails of´ver the use of the word "compressibility" for quite sime time.

 

1) Compressibility is a thing entirely different from what people use the word for:

It's the ability of air to compress (contrary to water* which is incompressible) under pressures.

Compressibility happens at all airspeeds, but usually isn't noticed and the effect is low when staying at lo airspeeds. You usually only take compressibility effetcs into account when considering airspeeds greater than Mach 0.3**.

What people are talking about when using the word "compressibility" is the backwards shift of center of pressure when going faster than Mcrit.

"Compressibility effect" is a term used in vintage papers about that phenomenon, but during that time, knowledge was generally little and confined to several islands of knowledge.

You'd best use the term Mach tuck (who is not related to Frair Tuck). It sounds cooler, too.

 

2) Aileron reversal is a function of a wing's torsional stiffness. Due to the way the Spit's wings were designed (basicly a D-shaped torsional box and an auxiliary spar to attach the ailerons to), the torsional stiffness isn't all too great (speaking in relative terms).

 

/smartassery

___

* Sidenote: If you're applying astrological pressures, water is compressible, too. But you'll probably have to travel to Jupiter that also has metallic hydrogen in it's...well, soil (for the lack of a better word).

** Kind of like using relativistic vs "classic" (newtonian) mechanics when considering velocities faster than about 0.3 times the speed of light.

[Legioneod]

3 minutes ago, Bremspropeller said:

 

Please excuse my smartassery, but I've been biting my nails of´ver the use of the word "compressibility" for quite sime time.

 

1) Compressibility is a thing entirely different from what people use the word for:

It's the ability of air to compress (contrary to water* which is incompressible) under pressures.

Compressibility happens at all airspeeds, but usually isn't noticed and the effect is low when staying at lo airspeeds. You usually only take compressibility effetcs into account when considering airspeeds greater than Mach 0.3**.

What people are talking about when using the word "compressibility" is the backwards shift of center of pressure when going faster than Mcrit.

"Compressibility effect" is a term used in vintage papers about that phenomenon, but during that time, knowledge was generally little and confined to several islands of knowledge.

You'd best use the term Mach tuck (who is not related to Frair Tuck). It sounds cooler, too.

 

2) Aileron reversal is a function of a wing's torsional stiffness. Due to the way the Spit's wings were designed (basicly a D-shaped torsional box and an auxiliary spar to attach the ailerons to), the torsional stiffness isn't all too great (speaking in relative terms).

 

/smartassery

___

* Sidenote: If you're applying astrological pressures, water is compressible, too. But you'll probably have to travel to Jupiter that also has metallic hydrogen in it's...well, soil (for the lack of a better word).

** Kind of like using relativistic vs "classic" (newtonian) mechanics when considering velocities faster than about 0.3 times the speed of light.

The reason people use it is because that is what it is called in the flight manuals and in reports.

[Quinte]

2 hours ago, ZachariasX said:

Them giving a different pictures does not really make them liars

It has nothing to do with being liars (some of them, though, might have embellished stories for entertainment purposes).

Pilots accounts are really marginally useful for two main reasons.

- Pilots themselves were under a lot of pressure, usually suffereing from PTSD, drugged as hell, and overall living violent combats that were happening really fast. Hence they often had a lot of trouble depicting the situation or the aircrafts involved accurately, even during or immediately after the facts (comparing multiple accounts of a single encounter show that. For exemple, during the first encounter between Ta 152s and Tempests, a tempest pilot described the Ta as a Bf-109E. Which is highly unlikely in 1945).

- Then memory itself can't be considered reliable. Memories are modified pretty much everytime they're accessed. People can actually believe something has happened to them even if it never did (and pretty important stuff too), and that's very easily induced.

 

Test reports are much more reliable, as long as they are taken for that they are: an approximate picture of the performance of a single aircraft, on one or a few days.

[7.GShAP/Silas]

Fish stories are a proud military tradition.

[MiloMorai]

Can't  wait to hear complaints that the 8 hmg of the P-47 can't knock out Tigers.?

[=RvE=Windmills]

22 hours ago, Legioneod said:

The thing about the Thunderbolt is that it really depends on what altitude you are at, anything below 10k and you'll be slower than everything but a Spitfire (very close in speed actually)

I'll post some charts in a bit though.

 

That's, actually a lot worse than I thought.

 

Well, hopefully it at the least handles well.

[PainGod85]

The P-47D at 2600 hp (64") will do 345 mph at SL, and this is with lower than optimum prop efficiency.

 

The original reduction gear the P-47D was delivered with was geared to give optimum prop RPM for the earlier, smaller airscrew. They never changed this reduction gear for any P-47D as it would've mandated tearing the engines apart and essentially rebuilding them with new parts.

Instead, they ended up refitting the planes with larger paddle blade airscrews, and the pilots could actually gain increased thrust by slightly reducing engine RPM - the higher prop efficiency more than made up for the slight loss in raw engine power.

This isn't exclusive to the P-47, either - the F4U, mounting a similar engine with the same prop could also benefit from it.

 

However, the P-47M did indeed receive a different reduction gear on its engine, and it could efficiently use the larger diameter airscrew at its maximum 2800 engine RPM.

 

TL;DR: Running R-2800-59 at 2700 RPM with an 'aftermarket' propeller fitted is actually a bad idea.

[Talon_]

Smart play with the Thunderbolt is climb up to 34,000ft and *start* your attacks from that altitude on the 109s and 190s at 25,000ft. You never see them on WoL of course but there's always fights on 1944 KoTA at that 25,000.

[MiloMorai]

The -57 in the P-47M was a 'C' engine while the D used the 'B' engine.

[PainGod85]

3 minutes ago, MiloMorai said:

The -57 in the P-47M was a 'C' engine while the D used the 'B' engine.

 

Exactly. The C type engines had hammer forged pistons and were generally reinforced to withstand the higher RPMs. 72" while using 100/130 grade fuel.

[MiloMorai]

Yes the 'C' engines were completely re-designed.

[Legioneod]

2 hours ago, PainGod85 said:

 

Exactly. The C type engines had hammer forged pistons and were generally reinforced to withstand the higher RPMs. 72" while using 100/130 grade fuel.

The B series could also achieve 70" with 150 fuel but it's very unlikely that we will ever see this in-game. The 9th never used 150 so we will get the standard 64" which is still good and will give us 2600hp.

 

What's interesting to me is the different critical altitudes of some of the P-47D blocks. I'm not sure if this was due to the different turbo speeds/ engine or maybe in part for the different prop used but it's very interesting.

 

Best bet in the P-47 is to stay high, don't be afraid to get down low though, a P-47 can still hold it's own on the deck.

3 hours ago, Windmills said:

 

That's, actually a lot worse than I thought.

 

Well, hopefully it at the least handles well.

It can roll, zoom, and dive better than most. Only thing that will outroll it is the 190 and only the 262 can outdive it.  Turning is never a good idea in the P-47, it can stick with 190s and even the rare 109 at certain speeds/altitudes, but it's best to just hit and run or BnZ.

 

The P-47 handles well at higher speeds and is a dream up high, it gets full power all the way up to around 30k ft depending on the block. The highest speed of the one we are getting is around 443 mph at 29-30kft.

Edited September 16, 2018 by Legioneod

[=RvE=Windmills]

1 hour ago, Legioneod said:

It can roll, zoom, and dive better than most. Only thing that will outroll it is the 190 and only the 262 can outdive it.  Turning is never a good idea in the P-47, it can stick with 190s and even the rare 109 at certain speeds/altitudes, but it's best to just hit and run or BnZ.

 

The P-47 handles well at higher speeds and is a dream up high, it gets full power all the way up to around 30k ft depending on the block. The highest speed of the one we are getting is around 443 mph at 29-30kft. 

 

I don't doubt it will be strong up high, but with how niche an arena that is I question its value as a fighter. There's nothing to escort/objectives or objectives up there. Hard to surprise anyone when you're pulling obvious contrails and it's easily mitigated by enemies just dropping down in alt. It might dive better but its trivial to dodge an enemy in a dive who you are aware of. Maybe combination of high speed turn/roll has a better chance of giving you that one shot? Though visibility over nose was awful in 46, severely impeding your ability to lead at these speeds.

 

I guess it's just the reality of how the sim works atm, but I'll stop being pessimistic now.

 

Now how about that groundpounding though.

[Legioneod]

1 hour ago, Windmills said:

 

I don't doubt it will be strong up high, but with how niche an arena that is I question its value as a fighter. There's nothing to escort/objectives or objectives up there. Hard to surprise anyone when you're pulling obvious contrails and it's easily mitigated by enemies just dropping down in alt. It might dive better but its trivial to dodge an enemy in a dive who you are aware of. Maybe combination of high speed turn/roll has a better chance of giving you that one shot? Though visibility over nose was awful in 46, severely impeding your ability to lead at these speeds.

 

I guess it's just the reality of how the sim works atm, but I'll stop being pessimistic now.

 

Now how about that groundpounding though.

Many people questioned it's ability as a fighter during the war as well, yet it proved itself time and time again. The P-47 isnt really a fighter that you can get in and get alot of kills with, it takes patience and knowledge of how to actually fly the aircraft in order to be successful.

 

The P-47 will never be the best fighter down low but it will still be able to handle itself when flown correctly. All of the qualities that it possesses up high are still applicable down low (except for the speed) It will still dive better than any German prop and will outroll everything but the 190, couple that with it's zooming ability and you have a potent fighter.

 

Basically just gotta follow a few rules.

1. Learn your aircraft.

2. Never try to attack from a disadvantage.

3. Never turn.

4. When in doubt, dive away/run.

5. Never pick a fight you can't win.

6. Don't get greedy. (greed is the number one killer of sim pilots imo)

 

These are pretty obvious rules that apply to almost every aircraft, as long as you follow them you should do ok.

Edited September 16, 2018 by Legioneod

[PainGod85]

3 hours ago, Legioneod said:

The B series could also achieve 70" with 150 fuel but it's very unlikely that we will ever see this in-game. The 9th never used 150 so we will get the standard 64" which is still good and will give us 2600hp.

 

What's interesting to me is the different critical altitudes of some of the P-47D blocks. I'm not sure if this was due to the different turbo speeds/ engine or maybe in part for the different prop used but it's very interesting.

 

The early P-47Ds had a less capable turbosupercharger.

Regarding different critical altitudes for the later P-47Ds, there you enter the time where it was uprated multiple times, and every time maximum permissible boost on the same engine is increased without any mechanical modification of the intake manifold, critical altitudes decrease as compressor RPM reach their maximum permissible number sooner as it needs to supply more air than at a lower boost.

[Legioneod]

51 minutes ago, PainGod85 said:

 

The early P-47Ds had a less capable turbosupercharger.

Regarding different critical altitudes for the later P-47Ds, there you enter the time where it was uprated multiple times, and every time maximum permissible boost on the same engine is increased without any mechanical modification of the intake manifold, critical altitudes decrease as compressor RPM reach their maximum permissible number sooner as it needs to supply more air than at a lower boost.

My question is why some of the earlier P-47s were faster at lower alt than the later P-47s with a higher critical alt?

[PainGod85]

34 minutes ago, Legioneod said:

My question is why some of the earlier P-47s were faster at lower alt than the later P-47s with a higher critical alt?

 

Do you have an example at hand?

[ZachariasX]

38 minutes ago, Legioneod said:

My question is why some of the earlier P-47s were faster at lower alt than the later P-47s with a higher critical alt?

Not sure what exact graph you are refering to, but one has to keep in mind that the Jug got progressively (even) heavier.

 

Look here:

 

ARMY AIR FORCES
MATERIEL CENTER
Wright Field, Dayton, Ohio
6 October 1944

Comparison of P-47D, P-47M and P-47N Performance

 

	P-47D	P-47M	P-47N
High Speed at S.L.	345	367	359
"        "      "  10,000	383	401	392
"        "      "  20,000	417	436	423
"        "      "  32,000	435	473	457
R/C at S.L.	3180	3960	3580
"   "  10,000	2920	3740	3500
"   "  20,000	2470	3300	3150
"   "  32,000	1100	2180	1840
Combat Radius	600	400	1310
Combat Weight	12,731	13,262	15,790
War Emergency Power	2,600	2,800	2,800

 

The high speed of the P-47D at 32,000 is estimated, otherwise all performance figures are actual. All power is at war emergency, airplane in combat condition.

 

You can see that speed is disproportinally higehr at high altitude, where the newer superchargers have more breath. dwn low, you're basically running on the first stage radial compressor, and that rating is about the same for same variants (while weight increased) until very late. You only have the better props offseting the weight penalty down low.

 

But as said, I should like to see the graph in question.

[Legioneod]

17 minutes ago, PainGod85 said:

 

Do you have an example at hand?

It was used for testing so the results may not be standard for every aircraft.

It was a D-22 with a R2800-63 (not the 59 oddly enough) It achieved 340mph at sea level, around 427 at 20k, and around 439 at 25k. after that it's performance dropped off.

10 minutes ago, ZachariasX said:

Not sure what exact graph you are refering to, but one has to keep in mind that the Jug got progressively (even) heavier.

 

Look here:

 

ARMY AIR FORCES
MATERIEL CENTER
Wright Field, Dayton, Ohio
6 October 1944

Comparison of P-47D, P-47M and P-47N Performance

 

	P-47D	P-47M	P-47N
High Speed at S.L.	345	367	359
"        "      "  10,000	383	401	392
"        "      "  20,000	417	436	423
"        "      "  32,000	435	473	457
R/C at S.L.	3180	3960	3580
"   "  10,000	2920	3740	3500
"   "  20,000	2470	3300	3150
"   "  32,000	1100	2180	1840
Combat Radius	600	400	1310
Combat Weight	12,731	13,262	15,790
War Emergency Power	2,600	2,800	2,800

 

The high speed of the P-47D at 32,000 is estimated, otherwise all performance figures are actual. All power is at war emergency, airplane in combat condition.

 

You can see that speed is disproportinally higehr at high altitude, where the newer superchargers have more breath. dwn low, you're basically running on the first stage radial compressor, and that rating is about the same for same variants (while weight increased) until very late. You only have the better props offseting the weight penalty down low.

 

But as said, I should like to see the graph in question.

The weight difference between the two blocks were marginal, they did use different engines though so that could be a reason. 

Also, it was testing so it may not reflect actual combat performance.

 

Here is the report.

http://www.wwiiaircraftperformance.org/p-47/p47-26167.html

 

Edited September 16, 2018 by Legioneod

[PainGod85]

4 hours ago, Legioneod said:

It was used for testing so the results may not be standard for every aircraft.

It was a D-22 with a R2800-63 (not the 59 oddly enough) It achieved 340mph at sea level, around 427 at 20k, and around 439 at 25k. after that it's performance dropped off.

The weight difference between the two blocks were marginal, they did use different engines though so that could be a reason. 

Also, it was testing so it may not reflect actual combat performance.

 

Here is the report.

http://www.wwiiaircraftperformance.org/p-47/p47-26167.html

 

 

Planes were often flight tested with bomb shackles installed, and the P-47's in particular were quite large.

The differences in the performance the D-22 you cited and the one you quoted from WW2AFP can be explained by measuring inaccuracies and/or the state of the plane, or a different prop being fitted.

 

 

The graph you posted gives you all the answers if you look closely:

 

I'll ignore the B model with its 2000 hp non-water injected engine as I'm pretty sure it was fitted with the less capable turbo.

The next three are test runs of the same plane fitted with different airscrews. You can see the massive difference the two paddle blade makes, and you can see the Curtiss 836 prop lose efficiency at high speed. meanwhile, the Hamilton airscrew ended up being an improvement in both climb and speed performance if you read the report associated with these test results.

 

Spoiler

 

http://www.wwiiaircraftperformance.org/p-47/P-47D_43-75035_Eng-47-1714-A.pdf

 

 

Now it gets interesting. 65 and 70" running 150 octane fuel...but with the crappy stock airscrew Curtiss aftermarket airscrew, bomb shackles and probably that fourth pair of guns.

 

There's no mention of bomb shackles on 75035, but they did say it was fitted with only six guns where no such mention was made for 26167. The lower speeds of 26167 at the critical altitudes of 75035 can thus probably be explained by lower drag of the latter because it was not fitted with bomb shackles or the fourth pair of guns.

 

Meanwhile, 26167 (a D-22, the first to be fitted with the universal wing):

 

Spoiler

 

Also, we can assume the later D-22 might have had a few more aerials than the D-10, so that's another probable cause of additional drag.

Edited September 16, 2018 by PainGod85

[=RvE=Windmills]

Would it be plausible to have multiple props as modification? Or did they settle on a single type at this stage?

 

70hg is off the table for continent based fighters regardless right?

[Legioneod]

14 minutes ago, Windmills said:

Would it be plausible to have multiple props as modification? Or did they settle on a single type at this stage?

 

70hg is off the table for continent based fighters regardless right?

D-28 only had one propr type iirc, and yes 70" is never gonna happen imo, though maybe one day.

We could potentially see different props as a mod, I think I've seen photos of D-28 with different props, though I think the standard was curtiss electric paddle prop.

 

The performance for the D-28 between 64" and 70" isnt that large, the D-28 could do 443 mph with 64" at 29k.

Ignore that top speed chart above, it has no relation to the D-28 in most regards though the speeds will be similar, just not at the same altitudes.

Edited September 16, 2018 by Legioneod

[Hoss]

Are those Monroe Q. Williams' archives?

 

Hoss

 

I used to talk to him on Hyperlobby when he played with 353rd.  His son and I have the same name, Monroe was a hell of a nice guy, he also knew my cousin in the AF. 

 

Cheers

 

Hoss

 

[DSR_A-24]

Speaking of Speed with different propellers, w/o pylons and power settings. I've already got that all figured out. 

P-47D-30 high speeds with Curtiss propeller.

345 0ft
383 10K ft
417 20K ft
*443* 29K ft
435 32K ft

There aren't any figures with the P-47D-30 using the Hamilton propeller but I'm sure we can assume the performance difference based of the P-47D-10 using the same engine settings(2600HP or 64/65"Hg). There is a 2% speed difference between the Curtiss propeller and Hamilton propeller.

345(352)
383(390)
417(425)
443(452)
435(444)

Now, the best case scenario P-47 would also include 150 Octane. A gain of 5"Hg from 65"Hg gives the P-47 another 2% increase in speed. So we'd be looking at a 360 mph at SL. Which is up to par with the Fw-190A8 and G14. Allowing us to fight at any altitudes. 

[GP*]

BoBP’s early access has been a whole bunch of airborne Rolls Royce and Mercs battling it out in a very proper, efficient, and gentlemanly manner so far. 

 

Regardless of its performance, it’s going to be a hell of a time crashing the party in a Challenger Hellcat with all 8 .50s blaring. 

 

(In case none of that made any sense, it’s one of those joke things you occasionally hear about. Sorry Crump, I couldn’t export it to .xls format.) 

 

 

[Farky]

17 hours ago, Windmills said:

Would it be plausible to have multiple props as modification? Or did they settle on a single type at this stage?

 

Not really. Standard propeller from P-47D-28 until end of production was Curtiss Electric. Last Thunderbolt produced with Hamilton Standard Hydromatic propeller was block P-47D-27-RE.

[ITAF_Rani]

 

[busdriver]

On 9/15/2018 at 8:35 AM, Bremspropeller said:

Compressibility happens at all airspeeds, but usually isn't noticed and the effect is low when staying at lo airspeeds. You usually only take compressibility effects into account when considering airspeeds greater than Mach 0.3**.

 

What people are talking about when using the word "compressibility" is the backwards shift of center of pressure when going faster than Mcrit. "Compressibility effect" is a term used in vintage papers about that phenomenon, but during that time, knowledge was generally little and confined to several islands of knowledge.

 

You'd best use the term Mach tuck (who is not related to Frair Tuck). It sounds cooler, too.

 

 

Interesting, Mach 0.3 is roughly 228 mph, 200 knots, or 366 kph. This Mach 0.3 threshold was never mentioned in my military training or airline training.

 

Aerodynamics For Naval Aviators chapter 3 High Speed Aerodynamics has a nice discussion about compressibility. Who knew that US Navy's Test Pilot School had such little knowledge. It is a fact that pilots/aviators will use words that make engineers cringe. I had a WSO (aero engineering PhD) tell me that my use/definition of the "P sub s equals zero curve," was wrong. I pointed out my verbatim quote in a universal AF reference manual. 

 

In the McDonnell Douglas F-4 Phantom, Mach tuck was emphasized as the tendency of the stab effectiveness to increase as you were slowing from supersonic to subsonic. It's the opposite of the slight nose down tendency as you accelerate through the transonic region.  So if you were running like a scalded ass ape, and decided you needed to make a hard turn/break turn, it was extremely easy to over G as the stab "dug in" (making the stick "tuck" into your lap as it were) if your speed was in the Mach .92 - .95 range.  A corollary hazard to Mach tuck was pulling the throttles out of AB in the transonic region.

 

As it relates to WWII aviation and the effects of high speed flight on flight controls, I'm comfortable sticking with compressibility.  To me it refers to the flight control flutter, buzz, stiffness or any other loss of effectiveness related to high airspeed.

[ZachariasX]

11 minutes ago, busdriver said:

it was extremely easy to over G as the stab "dug in" (making the stick "tuck" into your lap as it were) if your speed was in the Mach .92 - .95 range. 

What also happens at that speed is besides pressure points generally travelling backwards, that the foils are losing a great deal of lift, which in part is compensated by the a/c riding on the shock wave, creating some lift. At supersonic speeds, the air is not really flowing around an airfoil anymore, it is more like "bouncing off". partial supersonic airflow might cause an overbalancing of the controls. It is very interesting what you say. A good friend of mine flew the Mirage III and he said he usually wouldn't directly notice when the plane going supersonic. But given your statement, I will have to ask him again, more specifically.

 

[GP*]

4 hours ago, busdriver said:

 

Interesting, Mach 0.3 is roughly 228 mph, 200 knots, or 366 kph. This Mach 0.3 threshold was never mentioned in my military training or airline training.

 

Aerodynamics For Naval Aviators chapter 3 High Speed Aerodynamics has a nice discussion about compressibility. Who knew that US Navy's Test Pilot School had such little knowledge. It is a fact that pilots/aviators will use words that make engineers cringe. I had a WSO (aero engineering PhD) tell me that my use/definition of the "P sub s equals zero curve," was wrong. I pointed out my verbatim quote in a universal AF reference manual. 

 

In the McDonnell Douglas F-4 Phantom, Mach tuck was emphasized as the tendency of the stab effectiveness to increase as you were slowing from supersonic to subsonic. It's the opposite of the slight nose down tendency as you accelerate through the transonic region.  So if you were running like a scalded ass ape, and decided you needed to make a hard turn/break turn, it was extremely easy to over G as the stab "dug in" (making the stick "tuck" into your lap as it were) if your speed was in the Mach .92 - .95 range.  A corollary hazard to Mach tuck was pulling the throttles out of AB in the transonic region.

 

As it relates to WWII aviation and the effects of high speed flight on flight controls, I'm comfortable sticking with compressibility.  To me it refers to the flight control flutter, buzz, stiffness or any other loss of effectiveness related to high airspeed.

 

Busdriver, shouldn't you be on base waiting in line at the pharmacy right now, or checking out the latest deals at the BX?

 

I kid!

 

Bremspropeller is the guy who would interrupt the patch's BFM brief to say "sir...you said line of sight...didn't you mean line of sight rate?"

Edited September 18, 2018 by Go_Pre

[busdriver]

3 hours ago, ZachariasX said:

What also happens at that speed is besides pressure points generally travelling backwards, that the foils are losing a great deal of lift, which in part is compensated by the a/c riding on the shock wave, creating some lift. At supersonic speeds, the air is not really flowing around an airfoil anymore, it is more like "bouncing off". partial supersonic airflow might cause an overbalancing of the controls. It is very interesting what you say. 

 

 

ZachariasX my friend, I'll take your word for it.  I studied liberal arts in university.  Your post reminds me of a quote in Shaw's Fighter Combat, something about fighter pilots with a slide rule. Anyway the take away for me is watch out for those aero engineers.

 

Going supersonic was not noticeable (in the Phantom or the Viper), no burble, no bump, maybe a slight quiver of the airspeed needle. The Phantom cockpit got REALLY LOUD the faster you went because of the canopy frame and external mirrors. I remember a low level ride with an IP in the back. He told me to push the throttles to MIL...as we got to 600 KIAS at 500' AGL (There i was...fangs out, hair on fire...) I could tell the IP was yelling because I was yelling back at him..."What? What?" but the ambient noise cancelled out our words. Next thing I know the throttles magically came back to mid range. "Sir what did you say?" He replied, "Slow down."

 

I did a fair amount of Mach runs in the F-16 as the Wing FCF pilot, but that was above FL400. Transitioning through "the Mach" was unremarkable...it just did. When I would tell my backseater (enlisted personnel getting an incentive ride) they were now going supersonic, they usually responded, "I didn't feel or hear anything." So I'd say, "hang on, here it comes...KABOOM (that was me making the noise)." Followed shortly by, "Oh yeah...wait...was that you?"

 

46 minutes ago, Go_Pre said:

 

Busdriver, shouldn't you be on base waiting in line at the pharmacy right now, or checking out the latest deals at the BX?

 

 

 Too funny. Allow me to provide a translation for our 1G Comfy Chair Fighter Pilot brethren. Go_Pre is talking about the phenomena of military retirees outnumbering active duty folks on base, getting their prescriptions filled and shopping. As it turns out...I'm not a military retiree. But the joke is funny as hell to me. He could have easily asked when my shift at Wal-Mart or McDonald's starts (cause that's where a lot of old farts like me make a few bucks).

 

 

[Bremspropeller]

22 hours ago, busdriver said:

Interesting, Mach 0.3 is roughly 228 mph, 200 knots, or 366 kph. This Mach 0.3 threshold was never mentioned in my military training or airline training.

 

It can be all kind of velocities, depending on temperature, but yeah: It was pretty much a basic thing in my under- and post-graduate aerodynamics lectures in Aerospace Engineering.

It's where CAS and EAS start to diverge noticeably.

 

BD, did you get to fly slick winged Phantoms during RTU/OCU?

I wonder how much difference the slats made at high Mach and g. A friend of mine flew the F-4F and it appearantly was pretty easy to trash the airfame (close to 7000FH on most, so all kinds of fancy peace-time restrictions). He told me it was pretty easy to get your butt busted in the transonic range, pulling hard and have the slats deploy on you at 11 units AoA.

 

18 hours ago, Go_Pre said:

Bremspropeller is the guy who would interrupt the patch's BFM brief to say "sir...you said line of sight...didn't you mean line of sight rate?"

 

Yes I am that guy. And I'm proud of it.

There's also no rate of speed.

Yes, I AM fun at parties.

[GP*]

27 minutes ago, Bremspropeller said:

 

It can be all kind of velocities, depending on temperature, but yeah: It was pretty much a basic thing in my under- and post-graduate aerodynamics lectures in Aerospace Engineering.

It's where CAS and EAS start to diverge noticeably.

 

BD, did you get to fly slick winged Phantoms during RTU/OCU?

I wonder how much difference the slats made at high Mach and g. A friend of mine flew the F-4F and it appearantly was pretty easy to trash the airfame (close to 7000FH on most, so all kinds of fancy peace-time restrictions). He told me it was pretty easy to get your butt busted in the transonic range, pulling hard and have the slats deploy on you at 11 units AoA.

 

 

Yes I am that guy. And I'm proud of it.

There's also no rate of speed.

Yes, I AM fun at parties.

 

Haha, I'm sure you are! And to counter, unless I misunderstood your retort...LOS isn't a speed ;). 

[Bremspropeller]

Nah, rate of speed is a general term that is used often in casual conversation and makes my toenails do all kinds of impossible things. I won't elaborate, because...you know..the kids ☺️

[Gambit21]

20 hours ago, busdriver said:

 

ZachariasX my friend, I'll take your word for it.  I studied liberal arts in university.  Your post reminds me of a quote in Shaw's Fighter Combat, something about fighter pilots with a slide rule. Anyway the take away for me is watch out for those aero engineers.

 

 

 

I believe it was in Clancy's "Every Man a Tiger" that read about a Hornet test pilot who was nearly killed (or at least nearly lost his aircraft) due to a strange/non-intended departure that caused more than a healthy dose of pucker factor for said pilot. After making it back and landing with life and aircraft intact, he reported the departure to the engineer/s, adrenaline still spiked from the near loss of life/aircraft.

 

The engineers listened, expressionless, then shook their heads, made a scribble on a clip-board and turned around and walked away.

[busdriver]

5 hours ago, Bremspropeller said:

It can be all kind of velocities, depending on temperature, but yeah: It was pretty much a basic thing in my under- and post-graduate aerodynamics lectures in Aerospace Engineering.

It's where CAS and EAS start to diverge noticeably.

 

BD, did you get to fly slick winged Phantoms during RTU/OCU?

 

I'll take your word for it regarding the significance of the divergence of Calibrated and Equivalent airspeed. Once I got out of UPT, that divergence was of no use to line pilots. Sure, we had to spin the whiz wheel  (E6B slide rule) and complete an ICE-T problem for the annual instrument written test, but then that requirement went away too. 

 

You may appreciate the irony I'm about to offer...or not. In the Phantom community, the expression you're looking for is "hard wing" rather than slick wing. Hard wing refers to the lack of Leading Edge Slats (LES). And again generally speaking, a slick wing would refer to an airplane without external tanks or pylons (pylons for tanks or pylons for weapons). As it turned out, a totally slick hard wing Phantom had an issue with lateral stability at high AoA, so a hard wing with only inboard pylons was considered slick. I flew the unarmed RF-4C, a hard wing Phantom. It retained a weapons computer and wiring to carry bombs (that we never trained with) and in the early 80's the ANG modified their RFs and began training and carrying AIM-9Ps. The three years I spent flying it around Germany were the most fun a bachelor could have. When we flew BFM or DACT sorties we removed any/all external tanks but kept the inboard pylons...we called that...you guessed it, a slick airplane. The same applied in the F-16, a slick wing meant no tanks, no pylons.

 

I found quote I was thinking about. Shaw, page 392 Beware the lessons of a fighter pilot who would rather fly a slide rule than kick your ass! Commander Ron "Mugs" McKeown USN

 

[Bremspropeller]

EAS normally is of little signifigance for pilots - usually it's just a step in the ICET-conversion, and it's not needed using most rule-of-thumb CAS-TAS conversions (or even whizz-wheels).

It is very important for engineering, though. Lots of structural limitations are connected to EAS - including flutter.

 

Yeah, mixed those two terms (hard and slick - the hard wing should be slicker, though) up last night.

Did you guys ever get the bigger -17 motors in the RF-4C? The Marines got some -10s in their late model RF-4Bs. Must have been quite a ride - on a *slick* bird.

The whole recce-mission reads very interestingly - must have been one hell of a mission with virtually free reign on routings and objectives - especially in Europe.

Unfortunately there's relatively litte stuff to read about it.

The last couple of RF-4E airframes (GrAF and TuAF) interestingly did get LES. Not sure if they ever got the slatted horizontal stabilizer, though. IIRC the Marines retrofiteed their RF-4Bs (probably under Project Beeline) with the slatted stab. The Germans never put slatted stabs on any of their Phantoms (which makes the F-4F the only E-based airframe without them). Do you know if the later RF-4Cs got retrofitted? I know there was a more arodynamic camera-housing introduced at the later blocks.

 

On the Viper, would you go DACT without the tip ACMI-pod or a captive Sidewinder? I hear the extra mass on the tips was essential to provide extra-margin against flutter; but that could have been on another airframe with tip-rails.

 

BTW:

Mugs also crashed an F-4J during a DACT mission because he thought he was smarter than the NATOPS. That was before he got two kills and just after time he beat Col. Boyd, who he's referring to in the quote.