DEVELOPING THE XP-86
by Larry Davis
STRAIGHT WING XP-86
In 1939, the first operational airplane powered by a gas turbine engine was built. All previous powered airplanes had either inline or rotary cylinder engine, using either gasoline or diesel for fuel, and driving a propeller. Very simply, the gas turbine used its exhaust gas as power, commonly called thrust. In Nazi Germany, Ernst Heinkel had installed a gas turbine engine in his He-178 airframe, making its first flight on 27 August 1939. Across the Channel in England, British engineer Frank Whittle had one of his new gas turbines installed in a Gloster E.38-29 airframe. These two aircraft would ultimately lead to an entirely new concept which would revolutionize the aviation world - the jet aircraft.
In the US, little concern was paid to the new powerplant. The War Department was busy simply trying to catch up with the rest of the world regarding 'normal' airplane types. There was a war in Europe, and another heating up in the Pacific. And the US was far behind all the nations already involved with regards to high performance, propeller-driven aircraft. It wouldn't be until the development of the Lockheed P-38 and Republic P-47, that the US could expend money and energy on 'frivolous' things like gas turbines and jet aircraft. By that time it would be almost too late.When the P-51 Mustang (considered the best fighter in World War 2) was developed, the Germans already had an operational jet fighter ready to take on the Allies The Messerschmidt Me-262. The Me-262 was flying and ready for operations as early as 1943. Only stupidity on Hitler's part, and luck by the Allies, kept the German jets from decimating the Allied bomber forces. The Me-262 was a 150 mph faster than any propeller-driven airplane flying.
By 1942, a few US companies were becoming intrigued by the gas turbine. With engines borrowed from Whittle, Bell Aircraft Company constructed the XP-59 Airacomet, which made its first flight on 1 October 1942. But its performance was hardly earthshaking. It wasn't even on a par with contemporary prop fighter types. Lockheed also built a jet fighter, the XP-80. The XP-80 was powered by a DeHavilland Goblin turbine, and made its first ffight on 8 January 1944. Although the XP-80 broke the 500 mph barrier, it still was not competitive with German jets. Republic's XP-84 promised still greater performance, but it wouldn't fly until 1946.
North American Aviation (NAA) was also working on a gas turbine project. North American had experimented in a variety of different directions in an effort to increase the performance of the Mustang, including lighter weight, rocket assists, and jets. They installed a rocket in the aftercooler area of a P-51D. The rocket-assisted P-51D could attain a speed of 515 mph, but only for about a minute. Thoughts were given to a very radical P-51 with both a prop and a jet engine. This design concept had wings that were 'swept' forward. It was found that 'aft sweep' gave wingtip stall problems, so forward sweep was studied first. But the swept-wing P-51 never went beyond the drawing board as the wing suffered from a twisting divergence under load.
North American's engineers saw the future was in the alljet powered aircraft. On 24 August 1944, Ed Horkey talked with Ira Abbott about airfoil selection for a new jet-propelled, high-speed fighter design. They concurred that very thin wings would be required to avoid compressibility shock. Mr. Horkey was concerned about the lift and drag characteristics of such thin wings, and was informed that no recent data existed for any type of wing section with such small thickness ratios.On 22 November 1944, NAA initiated a design study (RD-265) for a jet fighter proposal. The design was straight forward in all respects, and used a lot of P-51 technology. It was just powered by a gas turbine. The flying surfaces, the wings and tail, were very similar to those found on the latest P-51 designs. The wing was of the latest laminar flow design, with straight leading and trailing edges. There were no'devices' added to the wings to either smooth air flow or increase lift.
The fuselage was short, rotund, and very smooth. The nose was open to induct air to the TG 180 gas turbine engine. The TG 180 was a General Electric license-built version of the DeHavilland Goblin gas turbine. The main problem was that the project (NA-134) was designed FOR THE NAVY. The Navy promptly ordered three prototypes of the NA-134 on 1 January 1945.
The US Army Air Force got interested in the North American Navy jet project in the Spring of 1945. On 18 May 1945, NAA received a letter contract to build three prototype aircraft for the Army, with the designation XP-86. The General Operational Requirements called for a day fighter of medium range, that could operate in both the escort and fighter-bomber missions, with a top speed in excess of 600 mph. This last item in the GOR was considered by many to be outside the scope of any jet designs at the time.
The XP-86 differed considerably from its Navy cousin, now designated the XFJ-1. North American refined the fuselage shape and deleted many of the things designed to aid in low speed performance that were required for aircraft carrier landings. The XP-86 wing had the same planform as the XFJ-1, but the airfoil was much thinner. On both the upper and lower wing seurfaces were the dive brakes, borrowed directly from the A-36A version of the Mustang. The fuselage had a much higher fineness ratio than the XFJ-1, and the intake was oval in shape. Power was the same for both aircraft - the GE TG 180 (J35). The TG 180 had an eleven stage, axial flow compressor, and offered 4,000 lbs of thrust.
The XP-86 would have a pressurized cockpit, hydraulic elevator and aileron boost, and had wingtip fuel tanks that could be jettisoned in emergencies. Armament was the standard for Army Air Force aircraft - six .50 calibre M3 machine guns in the nose, with 267 rounds per gun. The gunsight was the A-1 type, with a AN/APG-5 radar range finder. Under the wings, a pair of pylons could hold up to 2,000 lbs of bombs, drop tanks, or eight 5" HVAR rockets.The XP-86 was 35.5 feet in length, 13.2 feet in height, with a wingspan of 58.2 feet. With a maximum gross weight of 14,600 lbs. the TG 180-powered XP-86 was estimated to have a rate of climb of 5520'/min, a combat range of 1500 miles, a ferry range of 2240 miles when 170 gallon wingtip tanks were installed, and a service ceiling of 44,900'. But the speed was estimated to be only 582 mph at 10,000' - far below the GOR requlrement of 600+ mph.
On 20 June 1945, the mockup of the XP-86 was unveiled at the North American plant in Inglewood, California. Very sleek in its gloss Pearl Grey paint, the XP-86 mockup was quickly approved by Army Air Force officials. Photos of the mockup show that the aft section of the fuselage had its engine break about midway through the wing root chord. The fuselage was much sleeker than the rotund XFJ-1.
But North American officials knew that the lack of speed would eventually kill the XP-86 program unless something drastic took place, such as a much more powerful gas turbine or some way to reduce the drag encountered at speeds over 500 mph. It did! For many years, the advantages of sweeping the leading edge of the wing to reduce drag rise had been known. But the disadvantages of the swept wing were many, not the least of which was the loss of stability, especially at low speeds. The Germans had encountered this with the Me-262, which had a slight sweep to the outer wing leading edge. They found that by using a movable leading edge surface, commonly referred to as a 'slat', that many of the low speed stability problems could be overcome.
On 14 August 1945, North American Aviation received a research and development grant to develop a swept wing for the XP-86. Two weeks later a .23 scale model of a swept wing XP-86 was built. On 18 September 1945, the XP-86 model was wind tunnel tested. The results were exactly what North American and Army Air Force had been looking for. The swept wing lowered the drag rise and compressibility enough that it brought the XP-86 into the 600+ mph range, even using available gas turbine technology. And the leading edge slats appeared to solve any low speed stability problems encountered with the use of a swept wing. On 1 November 1945, Army Air Force approved the 'new' swept wing version of the XP-86. And the rest is, as they say, HISTORY!
ALUMINUM OVERCAST INTERCEPT
by Robert Krause
HOOOOOOOONNNKKK!!!
The klaxon got you again, didn't it! You hit the floor running with the unwanted extra shot of adrenalin you've just gotten. As you slam into the 'fire pole' at full tilt, the loudspeaker starts squawking "SCRAMBLE! SCRAMBLE! SCRAMBLE!" Down two full stories you go spinning around the fire pole, and faster than you want to go because you didn't get a good grip on the pole in your haste. SPLAT, your feet hit the rubber pad on the floor as you bottom out and almost turn your ankle. "Ha, Ha! Beat you again Sam!", you yell at your wingman coming down the pole right behind you.
Through the door and into the Alert Barn , you run to find your crew chief already at the bird starting the MD~3. 'That kid always beats me', you think, 'But then he didn't have as far to go, did he?' Up the kick steps you go, over the sill, and into the seat. The crew chief is right behind you and helps you into your chute, reminding you to make sure the lanyard is hooked. As he leaves, you finish strapping yourself in, don your helmet, and make a quick trip around the cockpit to check all the switches you had set earlier. Satisfied you nod to the chief, give the crank up signal and receive an "All Clear!"The MD-3 starts cranking the engine and when the tach indicates 10% you mash the ignition button and move the throttle around the horn. Eyes glued on the fuel flow gauge, you park it at 100 pph and watch for ignition. With a loud WHOOM, the J-47 lights off. Playing with the throttle to keep the temp within limits, you watch her begin to wind up. 'Good old manual start, it always works!'
"O'Hare Tower, November Kilo 11 with two for taxi. Standing by for scramble instructions." TWO checks in and the tower replies "NK 11, taxi runway 17, GCI departure, gate angels 34, vector 360, contact PAN FISH on primary, winds 345º at 10 knots. You're cleared for takeoff." You give the chocks-out signal, cob it out of the barn, turn 45º to the left, and cover the 75 yards to the runway as you read back the scramble instructions. Another 45º left turn puts you on the runway. You check the windsock and stop downwind waiting for Sam to catch up.
Sam gets the runup signal and you both go to MIL and check the gauges. You give Sam the BURNER signal and you go outboard, checking the cockpit once more, with one last check that the LOCK OUT BOX is off. You nod at Sam, release the brakes, and start rolling, giving Sam 1%. That's all he gets because he can cut it. Gear up, screens open, starboard to 360º, you enter the ragged overcast Steady on 36 º, you're climbing at 350 knots and you check your watch. 'Three minutes forty six seconds, not too bad!'
"One Two, go primary!", and you both switch to the GCI frequency. "PAN FISH, NK 11", "Two!" (Sam checks in). "NK 11, this is PAN FISH, go ahead." "PAN FISH, NK 11 with two, heading 360, climbing gate angels 34, ten north of Home Plate", you report as you pop out of the clouds and shake Sam loose. "Roger NK 11, PAN FISH 15 has contact, starboard 045 and report level." As you begin your turn, your attention centers on the radar. You turn all the shiny knobs off and all the dull knobs on, slowly coming up on the gain and down on the contrast. This 'tweaking' is a futile attempt to maximize the radar contact range, which usually doesn't work but makes you feel good because you've done it
"NK 11, your bogey is 45 port at 125 miles, heading 180, speed 320 knots." You acknowledge and attempt to visualize the coming intercept "This will be a level, 900 beam attack, with the target passing starboard to port Final attack heading 270." You report level at 340, come out of A/B, and set your speed at BUSTER. Several minutes later GCI turns you to 360 and tells Sam to go trailer. At this point, Sam drops five miles in trail and will begin to get seperate instructions from another controller for his intercept
A short time later your controller calls you. "NK 11, turn port 315. You have a heavy 15, starboard at 25. Set speed at 350 knots." "Roger", you reply as you steady out on the new heading and begin to look for the bogey on your radar. No contact yet, as expected, but you could hope anyway. Shortly you are turned to 270, putting you on your final attack heading. Time to arm it up!
You select 24 for the full pod of rockets. He did say it was a Heavy, remember, and you check your switches are HOT "Target 45, starboard 15 miles, check switches." You come heads up and realize you've just gone popeye in a layer of cirrus. "No joy!", you reply and go back into the scope looking for the target, but paying more attention to the radar horizon now. Nothing! You go to right sweep. 'Is there really something up here or has the controller mis-identified YOU?' No, you know better. He has YOU, it's just you don't have the target
"Target 45 starboard, 10 miles and level." Noth... WAIT! Is that it? There's a paint at 60 º starboard, about 8 miles out It has to be. Boy, am I hot (ahead of the line), you think as your eyes check the speed. 425 knots! Nice going Ace, got yourself into a fix not watching the airspeed. Now all you've got time is a hard check turn. "Contact!", you transmit as you pop the speed boards and make a hard 90 º right turn. Boards back in, you make another hard left turn back to the attack heading.
"Judy!", you say as you roll out and attempt to lock on. Darn, he's still 500 to starboard. Throttle to IDLE, turn right There, he's locked up at 5 miles. Put him on the left side for as long as you can stand, throttle to MIL, now center the dot HOLY COW! What a squirrelly dot! It's all around the circle as you yank and bank, trying to center it Two miles now.
The circle is shrinking but the B is sweep-jumping back and forth, making the steering dot jot along with it. Just average it out you think, and get the wingslevel. It's almost FIRE time. There, got it almost centered, heading 315, still hot, a quartering head-on attack! Now FIRE time. Wings level, dot passing through center right at the X (FIRE signal).
Suddenly out of the clouds appears the biggest airplane you've ever been this close to in the air! And it's on a collision course and level! Yes, you now remember what the controller said - LEVEL! "Alpa...." Stick in the gut, throttle to A/B, hard right! WOW, that was close! Up and over the huge B-36 you go. That thing realls is an Aluminum Overcast! No wonder the dot was so erratic. The radar couldn't decide where on the airplane to lock on - the nose, tail, props, or evenwhich prop! "Splash, breaking starboard, steady on 360.", you finally finish reporting. Even if the dot wasn't in the center at FIRE time on the radar, the ORI evaluator will have to give you a kill There's no way that 24 rockets could have missed something that big as close as you were. And I'm sure the bomber crew will also attest to that!
"NK 11, PAN FISH copies Splash One. Good work! Go starboard 120 now, Home Plate 120 at 65. Descend angels 20. This will be vectors for a GCI/GCA approach. Home Plate weather reporting ceiling 200 feet, and visibility 1/2 mile in snow and blowing snow, winds 345 º at 16 knots, gusting to 25, with deteriorating conditions. What are your intentions?
"PAN FISH, NK 11. I believe I'll give it a go", you calmly reply as you get ready for another northern tier, white-out approach and landing. But that's still another story!
SOME THOUGHTS ON WAR & HGHTER PILOTS
PAST AND PRESENT
by Carroll L. 'Stan' Stanton
Now that Harry 'The Horse' Evans (then a Lieutenant Colonel commanding the 12th FBS, 18th FBG) has made his last landing at that base in the sky, I (then also a LtCol and CO of the 67th FBS/l8th FBG) am left as the last commander who led his jocks on some of those Unauthorized Missions that Dee Harper wrote about in Sabre Jet Classics, vol. 2, no. 4. I feel it is TDW appropriate that I comment on some of those events.
In early 1953, 5th Air Force was finding it increasingly difficult to locate targets worthy of pre-planned air strikes. We all knew the communists were working feverishly preparing for their big spring offensive, and we were flying lots of armed reconnaissance missions. On this particular day, I led a flight of four F-86Fs on such a mission. Three F-86s carried two 500 lb bombs, and the last had two 1000 pounders. I took the heavy Sabre so it would be easier for the others to keep up.As we reached our assigned area, about 20 miles north of Heartbreak Ridge, we let down, spread out, and began our search. Our tactics were simple - keep each other in sight, stay between 5 and 10,000 feet, and keep changing headings and altitude or 'jinking'. Flying in a straight line would have meant a on-way ticket to a POW camp.
We had been there a few minutes when Number Four called out a bridge that hadn't been there the day before. I OKd his attack, but warned him to be wary of a flak trap. It was then that I saw something that was to change the course of the war. Just ahead of the flight were a number of large, about 15x30 foot, grey-green rectangles, stretching for about the next two miles.
My. first thought was they were tanks. But they were too big for tanks. Then it came to me. TROOPS IN THE OPEN! I tried to call Four off, but he was already in his dive. I headed west, called the others to join up, and started back to the enemy troops. We were about to attack the target of targets, later it would be The Mother Of All Targets!"
I called out the troop concentrations who were still holding their positions on the road. I also noted another, smaller group about a mile south of the larger group. The big bunch had two supply trucks in the middle of the column, and the smaller group had one truck, all covered with netting. I briefed the flight to make single bomb drops on each pass, and assigned sectors to spread the bombs over the length of the column.
Then I was on my run. When my 1000 pounders hit the edge of the road, a fireball covered one entire formation. For a quarter mile in each direction, the neat enemy troops disintegrated. The rest of my flight dropped as ordered, then set up a strafing pattern. The effect was devastating. Those enemy troops who could still move, broke for cover. As we were making additional passes, my guns suddenly stopped. When we returned to Osan, the crew chief found a loose battery cable, and the generator couldn't put out enough juice to fire the guns. Five minutes later it was fixed.
As soon as our debriefing was called in, I got a call from the JOC (Joint Operations Center) at 5th AF Headquarters. The caller wanted to know why I hadn't left the troops alone, reported the sighting to the JOC, and they would have got some napalm up there. Believe me when I say it's hard to be civil when asked a question like this in the heat of battle! I tried to convince him it was a 'fleeting target' of the highest order, and we were going straight back to finish the job!
And we did go back, this time with eight 500 lb bombs, which we once again placed equally along the length of the column. Then I did something that wasn't too bright, but I had to satisfy my curiosity. I made a single pass down the road - low but fast! It hadn't rained in weeks, but that road had mud (blood?) puddles from one end to the other. What a gory mess!
Returning home, we went to debrief, and the 'Mental Midget' from JOC was back on the phone. He said he doubted our claims because between our first and second attacks, he had diverted a flight from another wing and they found nothing. What did he expect, the enemy troops to stand up and wave red flags? Of course our guys found nothing. They didn't know precisely where the troops were. And the enemy sure as hell wasn't going to give away their position again!
We estimated conservatively, that we had killed 1,000 men. We had left the enemy to bury their dead and care for the wounded. We had neutralized an army which was to attack our east flank. Now there was no attack. No one will ever know how many American GIs would have died if we hadn't creamed that column. I wonder if that JOC guy looked up our claims when the predicted date for the enemy offensive came and went - and all was quiet on the eastern front.
I think it was two evenings later that Harry Evans came in. I had never seen him so excited. Both Harry and I had been there almost a year, and excitement didn't come easy. Harry had seen an ammunition train stranded a short distance from a tunnel (and safety from our bombs) just north of the 38th Parallel. The bad guys were trying to unload it by hand, and it was going to take a long time. Harry's flight saw this returning to base with no ammo. This is where Dee's story began and I'll add to it
When my flight arrived over the train, Harry's was just leaving again. It was now almost pitch dark. It was obvious we were setting ourselves up for a mid-air collision. That would have really ripped it! I took control and assigned 'holding quadrants, then called individual aircraft in and out of the target area. When I hit Bingo fuel, Harry was back and took over. let me say, I've never seen a fireworks display that comes close to the show that night. Burning ammo flew thousands of feet into the air, and secondary explosions were everywhere. That night we denied the communists their main supplies for the planned offensive against our west flank. We destroyed hundreds of tons of ammunition, and once again, the attack just didn't happen.
The enemy leaders were seriously demoralized. Their troops were gone in the east, and their ammo was gone in the west. They couldn't move anywhere in daylight because our F-86s were covering North Korea from the Yalu to the battle line. Most importantly, it was rice planting time. If they failed to get the rice in the ground, mass starvation was a certainty in the fall and winter. They HAD to get the F-86s out of the skies. They had only one course of action - seek a truce.
If our negotiators knew what the F86 pilots knew, they could have named their own terms. The Communists were beaten. All the fighter-bomber jocks knew it So we were in no mood to celebrate when we got the order to stand down from combat ops. With total victory in sight, we were going to negotiate an armistice that would allow the enemy to rebuild and rearm. A familiar pattern which would repeat itself in Vietnam and Desert Storm. Will we ever learn?
There is something truly magnificent about flying single seat fighters. You kick the tires, light the fire, then, with that little darling strapped to your butt, you and your wingman become the modern reincarnation of the knights of old. Back on the ground, there are no secrets among flight members. Everyone knows who cut it and who didn't. Among those who could, there is respect and loyalty as in no other group.
In many headquarters there seems to be a clique convinced they can do your job better than you can. These people can be dangerous when they won't listen to the guys who know. As an example, in spite of our complaints, our napalm cans had the ballistics of a grand piano. The only way to hit anything was to 'scrape off' the cans on the target. Try that in the face of heavy ground fire! lots of luck!
We lost over 53,000 men in Korea. That's 53,000 young sons, husbands, friends and lovers. Laid head to foot, that's over 70 miles of seven foot coffins! I will never understand why these heroes seem so easy to forget. But I'll say this about that war - I could never hope to serve with a finer group of men. They were loyal and couraegeous. And could damn well hit the target with a pair of bombs!
Well Harry, How'd I do?
RADAR LOCK-ON
HAROLD O. CHITWOOD
Major General John Giraudo remembers him as a "....young F-86 jock Lt. I had in the 25th squadron (51st FIW)... (he) turned out pretty good, didn't he?"The distinguished looking gentleman in our portrait did, indeed, turn out pretty good. Harold 0. Chitwood, 64, was featured in the May 1994 issue of Delta Airlines' SKY MAGAZINE. The article (featuring a full page color version of our portrait) begins with the following paragraph:
Harold 0. Chitwood, the soft-spoken CEO if Atlanta-based Gold-Kist, Inc., has flown F-86 combat aircraft in the Korean War, scuba-dived in exotic tropical locales, and caught 150 salmon in six days off the coast of Alaska. "Its a matter of how hard you want to work, and how many you want to catch," he says.
Harold is, of course, a member of the F-86 Sabre Pilots Association, and according to a note he dropped to General Giraudo, he plans to retire in October of this year. He intends to slow down his business activities and play a little more golf. He modestly insisted to General Giraudo that our RADAR LOCK-ON not leave out someone far more deserving.
Your editors were justifiably proud to find that one of our association members had achieved success in an industry which, at first glance, might seem like an unlikely career choice for a fighter pilot. On the other hand, successful fighter pilots have always been aggressive, willing to take prudent risks,
Innovating, and team players. These are qualities which contribute to success in any endeavor. Our association numbers amoung its members congressmen, business executives in many industries, astronauts, doctors, lawyers, CPAs, military members, etc., etc. The list goes on and on. We'll bet most of them would credit their fighter experiences as a prime reason for their successes.
In the case of Harold 0. Chitwood, Gold-Kist is a farm cooperative controlled by its farmer members. With more than $1.4 billion in sales in 1993, it has some 14,000 employees, 24,000 active members, and about 50,000 equity holders. Company policy is guided by a nine-member board, and this board appoints a Management Executive Committee, headed by a CEO (Chitwood), who exercises day-to-day management responsibility over the company and its enterprises. The Gold-Kist poultry group, which accounts for two-thirds of corporate sales, is the second largest poultry producer in the USA. Its average weekly output of 13.5 million broilers goes mainly to fast-food outlets, although the Young 'N Tender brand can be found in many supermarkets. Reflecting his fighter pilot beginnings, Harold is quoted in Delta's magazine as saying, "I like to be where the activity is going on, and where the action is. That's what I did early in my working career for the company, and what I like to do now."
Harold 0. Chitwood, Sabrejet Classics is proud to spotlight you in our radar beam, and we wish you continuing success and happiness in retirement. We hope you'll join us at future Sabre Pilots reunions.