Fighter: Flop or Not

[Shortround6]

Huh? The P-80/F-80 was similar in speed...

Similar is not the same, aerodynamic loads go up with the square of the speed the loads at 600mph are 13.7 % higher than at 560mph not 7%.
I would also note the early P80s (April 1945) were red lined at 560mph or Mach 0.80. which ever was lower at a given altitude. in other words max speed at level flight at sea level was also the max dive speed at low altitude. This was in the pilot's manual. this restriction may have been increased later?

I was mostly using the F-80 as a comparison... it was considerably lighter.
True enough, but if they were going for a new design, why not try and go lighter?

Please look at intended use of aircraft and some of the details. The F-80s grossed at 14,000lbs with wing tip tanks. Even an early F-84 was allowed a gross weight of over 19,600lbs. F-84B could not only carry the tip tanks (which were larger) but could carry a pair of 1000lb bombs AND eight 5in HVAR rockets.

to do this you need larger heavier landing gear for one thing. For another the engine in the F-84 was over 500lbs heavier than the engine in the F-80. This also translates into heavier structure and landing gear to support it.
F-80s were eventually modified to carry heavier loads (got uprated engines to do it) but by the time the F-80C was rated at 16,856lbs the F84-D was only a few months from being delivered and would be rated at 20,076lbs. About 14 months after the F-80C was being delivered the F-84E was being delivered with a max gross of over 22,000lbs.
The F-84 was always a more capable aircraft for ground attack than the F-80 and once they got the engine to deliver over 4000lb thrust they loaded way more fuel onto it for penetration/escort missions.
Designing a lighter airframe near the start of the program to suit the low powered engine would have meant throwing the whole thing out and starting over once the engine problems were straightened out.

 

[Zipper730]

Similar is not the same

True

I would also note the early P80s (April 1945) were red lined at 560mph or Mach 0.80.

The F-84 could reach 600 off the bat?

The F-80s grossed at 14,000lbs with wing tip tanks.

From what I get...

• F-80A
  • OEW: 7920 lbs
  • Loaded: 11700 lbs
  • Tip-Tanks: 14000 lbs
• F-84B
  • OEW: 9538 lbs
  • Loaded: 16475 lbs
  • Tip-Tanks: 18954 (estimate based on fuel load)

Difference is 1618 lbs OEW, 4775 lbs loaded, and 4954 with tanks

• F-80B
  • OEW: 8176 lbs
  • Loaded: 12200 lbs
  • Tip-Tanks: 16000 lbs
• F-84C
  • OEW: 9662
  • Loaded: 16584
  • Tip-Tanks: 19063 lbs

Difference is 1486 lbs OEW, 4384 lbs loaded, and 3063 with tanks...

• F-80C
  • OEW: 8420 lbs
  • Loaded: 12200 lbs
  • Tip-Tanks: 16856 lbs
• F-84D
  • OEW: 9860 lbs
  • Loaded: 16862 lbs
  • Tip-Tanks: 19341 lbs (estimate based on fuel)

Difference is 1440 lbs OEW, 4662 lbs loaded, and 2485 lbs with drop-tanks.

The difference was worse from the start, but it's still substantially heavier even empty.
Ironically, one of the problems might very well have been more that the wings were too small. The wing loading figures are considerably heavier for the F-84 than the F-80.

The F-84 was always a more capable aircraft for ground attack than the F-80 and once they got the engine to deliver over 4000lb thrust they loaded way more fuel onto it for penetration/escort missions.

The F-84 was primarily designed as a fighter with a 705 staute-mile radius, a top speed of 600 mph, with a J35, and 6 x 0.50 or 0.60 caliber.

While the J35 matured much slower than the J33, the weight of the engine didn't necessarily need to add quite as much weight to the design as it did. The FJ-1 Fury for example, using the same engine managed to weigh in at 8843 empty operational, and managed a radius of 750 nautical miles.

 

[Shortround6]

True
The F-84 could reach 600 off the bat?

Close enough, 1st XP-84 flew in March of 1946, During testing it hit 592mph at sea level. 2nd XP-84 first flew in aug 1946, On Sept 7th 1946 it set a record of 611mph at sea level, the same day a GLoster Meteor hit 616mph at sea level using almost double the power.

• F-80A
  • OEW: 7920 lbs
  • Loaded: 11700 lbs
  • Tip-Tanks: 14000 lbs
• F-84B
  • OEW: 9538 lbs
  • Loaded: 16475 lbs
  • Tip-Tanks: 18954 (estimate based on fuel load)

Difference is 1618 lbs OEW, 4775 lbs loaded, and 4954 with tanks

Not sure why you are estimating, the weights are given in the SAC sheets. Late dash model B had a gross weight of 19,689lbs not including 400lbs of ATO rockets. Take off weight was often limited by available runway.

• F-80C
  • OEW: 8420 lbs
  • Loaded: 12200 lbs
  • Tip-Tanks: 16856 lbs
• F-84D
  • OEW: 9860 lbs
  • Loaded: 16862 lbs
  • Tip-Tanks: 19341 lbs (estimate based on fuel)

Difference is 1440 lbs OEW, 4662 lbs loaded, and 2485 lbs with drop-tanks.

again, no need to estimate. Early F-84D had a max gross of 20,076lbs per the SAC sheet, late dash number Ds were allowed 20, 877lbs but that may include 4 ATO rockets.

While the J35 matured much slower than the J33, the weight of the engine didn't necessarily need to add quite as much weight to the design as it did. The FJ-1 Fury for example, using the same engine managed to weigh in at 8843 empty operational, and managed a radius of 750 nautical miles.

I wish you would compare apples to apples and quite bringing in squash or rutabaga. First flight of the XFJ-1 was Sept 11th 1946, four days after the XP-84 did 611mph. it carried 50rpg less ammo and more importantly, NEVER carried under wing loads (bombs or rockets). It also used an unpressurised cockpit and not very satisfactory cockpit heat. F-84s had pressurised cockpits and automatic cockpit heat.
I would also note that the FJ-1 did NOT weigh 8843lbs empty operational, it weighed 8843lbs empty. Granted the weights for the various F-84s are EMPTY weights and not empty operational (which at this point in time for US aircraft was called basic weight), both types of plane could add over 500lbs of equipment (like guns) to get up to basic weight.
You also might want to check out the FJ-1s wing loading with it's 221 sq ft wing (85% the size of the F-84 wing) Wing loading compared to an F-84 depends an awful on on how much fuel each plane is carrying.

And please quit quoting "radius" unless it is operational radius as it only confuses things. Radius is NOT 1/2 of range. operational radius will include combat allowance and reserve for finding home field at the very least (sometimes 10% of initial fuel) , they often include warm-up, take-off and climb to some sort of operational altitude. I would also note that the F-84s clean were slightly faster than the FJ-1 despite the larger wing and greater weight.

 

[Zipper730]

Close enough, 1st XP-84 flew in March of 1946, During testing it hit 592mph at sea level.

Okay

Not sure why you are estimating

Because I couldn't figure out if the MTOW figures were based on fuel, oil, armament, drop-tanks, or other stuff too. So I basically computed the weight of the fuel out.

Ironically, the correct figures show an even greater difference in weight between the two planes.

I wish you would compare apples to apples and quite bringing in squash or rutabaga. First flight of the XFJ-1 was Sept 11th 1946, four days after the XP-84 did 611mph.

I based it on the fact that both planes flew using the same engine and flew in 1946

it carried 50rpg less ammo and more importantly, NEVER carried under wing loads (bombs or rockets).

I didn't factor in the ammo (I didn't even think of that), though you make a good point about the under-wing loads (I never really understood why, considering the plane could pull over 6g). Regardless, the FJ-1 was navalized, requiring a stronger lower fuselage, landing gear, and arresting gear (ironically it did not have folding wings, but had a strange kneeler wheel instead).

It also used an unpressurised cockpit and not very satisfactory cockpit heat. F-84s had pressurised cockpits and automatic cockpit heat.

How much does cockpit pressurization and stuff cost in weight?

I would also note that the FJ-1 did NOT weigh 8843lbs empty operational, it weighed 8843lbs empty.

And OEW would include the weight of the radios and electronics, the guns but not ammo, and the pilot and equipment? I'm not sure if oil is factored in now, but I don't think it was factored in 1945-1950...

Granted the weights for the various F-84s are EMPTY weights and not empty operational (which at this point in time for US aircraft was called basic weight), both types of plane could add over 500lbs of equipment (like guns) to get up to basic weight.

That's why there were two empty figures?

And please quit quoting "radius" unless it is operational radius as it only confuses things.

The aircraft's listed combat range was 1496 nm, so... under that term I figured it'd be an exception whereby the combat radius is 1/2 the combat range. Normally in the era of propeller planes it was like 1/3 ferry range.

 

[Shortround6]

Empty weight did NOT include guns, oil, trapped fuel and for some WW II planes, the gun sight , pyrotechnics (flares) and oxygen and/or oxygen equipment.
Depending on date or service (Nation) the radios were not included so you really have to be careful and not make assumptions as to what was included.

Ferry range was almost NEVER used to figure operational radius. Some planes had some or all guns removed for ferrying. SOme planes could use much larger drop tanks for ferrying than they were allowed to use for combat missions ( even if they kept the guns they didn't fly with ammo) SOme planes may very well of operated at 1/3 of the ferry range but that is much more of a coincidence that a general rule.

And again, different services figured radius differently. US Navy wanted the planes to have 1 hour worth of fuel as a reserve (at most economical) in order to find the carrier if there were problems, que up for landing and then land, and if there is a crash of an early plane in the que the remaining pilots were damn glad they had that extra fuel. Fighters in europe often figured a much shorter reserve allowance. Their landing field wasn't moving, an single crash didn't take the whole field out of service and/or there were a number of other airfieds only a few miles away.

I would note that for the Navy FJ-1 Fury they were figuring combat radius including 15 minutes of combat at full power while the Air Force was figuring 20 minutes of combat at full power. What is that 5 minutes of full power worth in miles on the cruise back??? There may be differences in other allowances (both planes had a planned 10% reserve of original fuel but both planes did carry a very similar amount of fuel at least internal. )

Some people estimated the pressure cockpit on a 109 or Spitfire was around 200lbs but then they weren't using the same pressure levels in those aircraft?

 

[Graeme]

Still....not a flop in my opinion. In fact the more I read about the Thunderjet, the better it gets. Still fighting wars in 1973...

 

[Graeme]

The F-84 was primarily designed as a fighter

You keep repeating this but seem to forget that most of those early jet fighters ended up dropping bombs till better engines and airframes came along...

 

[Graeme]

And the Thunderjet continue to improve...especially with the D model...

 

[Shortround6]

I am not sure that is right either. But I would note that the US was not interested in very many specialized role fighters. While night fighters or all weather fighters as they would come to be known were pursued the US (both Air Force and Navy) were more interested in general purpose "fighters". That is ones that could also bomb/strafe/carry rockets rather than daylight only interceptors. Granted it sometimes took a while before the desired armament caught up with the airframes.

 

[Shortround6]

I would also note that between VJ day in Aug 1945 and Dec 31st 1949, just about 70 different jet, turbo-prop and rocket propelled aircraft made their first flights around the world. Some were research aircraft and many remained one (or two) "offs" and just because they were built doesn't really mean they were in any way reflective of the main thrust of thinking at the time.

XP-79, built to ram enemy aircraft.

crashed on first flight.
XP-85

Plan for B-36 to carry it's own escort fighter. Trying to hook back onto the B-36 proved a lot more difficult than it had about 15 years earlier.

Fads and theories came and went

First flight July 15, 1947 but didn't get very far.

One can certainly find a lot of "flops" out of this collection of aircraft. The F-84 wasn't one of them.

 

[Elvis]

All I know is that my dad, who was USAF '45-'65, had a high regard for the F-84.
He thought it was a better aircraft than most gave it credit for. According to him, it was taken out of service (front line, maybe?) too soon.

 

[Zipper730]

Empty weight did NOT include guns, oil, trapped fuel and for some WW II planes, the gun sight , pyrotechnics (flares) and oxygen and/or oxygen equipment.

What was covered under OEW at the time...

Ferry range was almost NEVER used to figure operational radius.

That's correct, but combat range would simply be 2 x combat radius?

And again, different services figured radius differently. US Navy wanted the planes to have 1 hour worth of fuel as a reserve (at most economical) in order to find the carrier if there were problems, que up for landing and then land, and if there is a crash of an early plane in the que

This is not to criticize you, but it's actually spelled "queue"

Fighters in europe often figured a much shorter reserve allowance.

What was the typical allowance?

I would note that for the Navy FJ-1 Fury they were figuring combat radius including 15 minutes of combat at full power while the Air Force was figuring 20 minutes of combat at full power. What is that 5 minutes of full power worth in miles on the cruise back???

Good point, but what does the shorter loiter times yield?

Some people estimated the pressure cockpit on a 109 or Spitfire was around 200lbs but then they weren't using the same pressure levels in those aircraft?

What pressure levels were used?

I am not sure that is right either. But I would note that the US was not interested in very many specialized role fighters. While night fighters or all weather fighters as they would come to be known were pursued the US (both Air Force and Navy) were more interested in general purpose "fighters".

That's generally true. The US Navy would at some point (late 1940's to early 1950's?) listed three categories of fighter planes

• All-Weather Interceptor
• Night Fighter
• General Purpose Day Fighter

 

[pbehn]

What was covered under OEW at the time...
That's correct, but combat range would simply be 2 x combat radius?
This is not to criticize you, but it's actually spelled "queue"
What was the typical allowance?
Good point, but what does the shorter loiter times yield?
What pressure levels were used?
That's generally true. The US Navy would at some point (late 1940's to early 1950's?) listed three categories of fighter planes

• All-Weather Interceptor
• Night Fighter
• General Purpose Day Fighter

That's a pretty good amount...
That's one of those bizarre legends that won't die: The XP-79 was originally built with hypergolic rocket-fueled engines, and featured angled-armor in the wing's leading-edge.

When the design became the XP-79B, the rockets were replaced with a pair of J30's, and the oxidizer was no longer needed: The fuel became high octane gasoline, or early jet-fuel.

The ramming thing might have been a nickname or a sales-pitch but it'd be stupid to try it...

• The airplane doesn't use traditional rudders but split brakes that deploy asymmetrically: These are controlled by airflow-controlled valves in the wing-tips. Do you really want those to get fouled up?
• The XP-79B used jet-powered engines and they'd get fodded up

Because the F9C was docking with an airship flying much slower; the plane was simply too light to not be affected by turbulent airflow off the B-29 test plane: The F-80C did it fine.

The SR/A1 was actually a magnificent fighter plane despite it's size.

No, awhile back I agreed it wasn't a flop, though I think it could have done better in building an air-to-air fighter-plane.
None had been designed for air-to-air combat? I sense some economy of truth here...

All the listed aircraft were conceived during WWII as fighters. As for armament: The F9F and F2H were both cannon equipped, the USAAF & USAF were reluctant to use 20mm and stayed with 15mm/0.60 cal for some time.

WTF? how many books are needed to reply to this?

 

[XBe02Drvr]

WTF? how many books are needed to reply to this?

Just one: "My First Book of Trolls" from Golden Books Press.

 

[XBe02Drvr]

WTF? how many books are needed to reply to this?

Maybe one other: "The Trigonometry of Obtuse Angles" by Pythagoras.

 

[pbehn]

Maybe one other: "The Trigonometry of Obtuse Angles" by Pythagoras.

It reminds me of this.

A pansy who lived in Khartoum
Took a lesbian up to his room,
And they argued all night
Over who had the right
To do what, and with which, and to whom.

I have no idea whos post is quoted, what they actually said, or even in some cases what the subject is.

 

[XBe02Drvr]

It reminds me of this.

A pansy who lived in Khartoum
Took a lesbian up to his room,
And they argued all night
Over who had the right
To do what, and with which, and to whom.

I have no idea whos post is quoted, what they actually said, or even in some cases what the subject is.

Dithery dithery doom,
An elephant's here in the room,
What can I say,
He just wants to play,
Dithery dithery doom.

 

[Zipper730]

WTF? how many books are needed to reply to this?

I shortened it: The questions involved basically cover what was defined as OEW at the time, effects of loiter time on range (even generalized rules), and combat time on range (even generalized rules).

The rest weren't really entirely questions: Some were answers, or statements...

 

[Zipper730]

All I know is that my dad, who was USAF '45-'65, had a high regard for the F-84.

That's pretty interesting? What variants did he fly by the way?

Also, what did he like about it?

 

[Shortround6]

ANd here is where we run into problems, "OEW" seems to be term for civilian aircraft and perhaps modern ones at that.

From Wiki:
Operating empty weight ('OEW') or 'Basic operating weight' or 'Empty Operating Weight' as is most commonly known is the standard basic weight for any particular series or any particular configuration. The aircraft is periodically weighed and its weight is listed with each structural modification order, or any configuration order which may alter the 'Empty Operating weight.' The EOW only includes all fluids necessary for operation such as engine oil, engine coolant, water, hydraulic fluid and the unusable fuel volume as calculated and then any extra fixed operator items and optional equipment required for flight. From there, 'any' weight 'Added' to the aircraft is the Total Payload, above the EOW, which consists of (a) Cargo (b) luggage (c) Passengers and Crew (d) stores (e) service load such as meals and beverages (f) Fuel load. The operating empty weight (OEW) is basically the sum of the manufacturer's empty weight(MEW), standard items (SI), and operator items (OI). all additional 'weight' added is computed for weight, Arm, moment calculations to determine the center of gravity."

Now in WW II for most aircraft the engine oil was NOT included in the empty weight or "trapped" engine oil was included in the "Basic" weight as engine oil was consumed at several gallons per hour. However the amount of oil needed for a flight/mission was included in the loaded (or payload) weight for American planes, but not the "light" weight for British planes. Guns were often included in "basic" or "light" categories but NOT in the empty or tare weight categories.
Gun mounts/turrets were included in the "basic" or "light"categories however. Ammo was listed in the loaded category.

Trying to use modern definitions/terms for 50-80 year old aircraft leads to confusion as the old data sheets use different terms/definitions. Trying to force old data into new definitions doesn't always work.