Night fighter! US Hornet pilot rates the combat effectiveness of the Grumman F7F-3N / 4N Tigercat

Former US Marine Corps Hornet pilot Louis Gundlach takes an in-depth look at the ultimate US twin-engine propeller night fighter, the formidable Grumman F7F-3N / 4N Tigercat.

            The Grumman F7F Tigercat, like the F4U Corsair before it, was an excellent fighter- bomber that found its way into Marine Corps squadrons due to a lack of carrier suitability.  The first Marine Corps Tigercats were introduced at the end of World War II and were single-seat day and night fighters, but the aircraft did not see action during the conflict.[1]During the five year period between World War II and the Korean War, the F7F series continued to develop with day fighters remaining single-seat and night fighter versions adding an aft position for the Radar Operator (RO).[2]  When the Korean War began the F7F-3N and F7F-4N were the night fighter versions of the Tigercat in use.  The standard F7F-3 day fighter was equipped with a single seat for the pilot and four .50 calibre machine-guns in the nose, along with four 20-mm cannon in the wing root.  The F7F-3N added an additional seat for the RO and removed the .50 calibre machine-guns to make room for the SCR-720 radar.  The main difference between the F7F-3N and the F7F-4N was the SCR-720 radar and controls were replaced by the APS-19 radar system. The F7F-4N also had strengthened wings and landing gear for improved carrier use.  The F7F-3N and 4N were eventually used by a limited number of U.S. Navy squadrons onboard Midway class carriers.[3]  The Marine Corps did not deploy their Tigercats to Navy carriers operationally.  Along with the F4U-5N, the F7F-3N and F7F-4N were the primary night fighters utilized by the VMF(N) squadrons in the early part of the Korean War.  (VMF(N) stands for V-Fixed Wing, M-Marine, F-Fighter, (N)-Night).[4]

F7F-3N in 1946

            The F7F-3N and 4N were large aircraft for the time, weighing over 21,000 pounds gross weight without ordnance.  Their max take-off weight was over 25000 pounds.  The aircraft was equipped with a pair of Pratt and Whitney R2800-34W engines that each produced 2100 horsepower .[5]  The 3N and 4N were slower than their day fighter counterparts due to the extra weight of the radar equipment and extra crewman.  The 4N’s max airspeed in level flight at sea level was 313 knots and it had a ceiling of 37,600 feet.  Compared to the performance figures of the F7F-2N, the reduction is easily noted.  The F7F-2N had a max speed of 402 knots at sea level and a ceiling of 42,000 feet.[6]  The F7F series had lift limit of 6 positive Gs and 2.5 negative Gs.  The F7F aircraft had a wingspan of 57’6” and was almost 45 feet long.  The 3N and 4N models were over 15 feet tall at the tail.  The 3N and 4N also had a range exceeding 1000 miles.[7]  F7F-3s, equipped with drop tanks flew non-stop from Marine Corps Air Station (MCAS) Cherry Point in North Carolina to MCAS Miramar in San Diego California on several occasions.  The 3Ns and 4Ns carried 80 pounds less fuel and weighed more than the day fighter version, but the advertised range of 1780 miles on internal fuel was still impressive on the night fighter versions.[8]

(Appendix 4 – Pictures of F7F-3N, RO station, Pilot Instrument panel, and RO radar panel.)

Ordnance

The F7F-3N and 4N carried the same ordnance as the F4U-5N.  It was equipped with four 20mm cannon and could also carry eight ATARS or HVAR rockets.  The Tigercat could carry 4,000 pounds of bombs with a 2000 pound bomb hung on the centerline and 1000 pound bombs or smaller being hung on the inboard wing bomb racks.[9]  The centerline station and the wing stations could also carry the 11.75 inch “Tiny Tim” rocket, but this large rocket was not used operationally by the Marine Corps.[10]  The normal combat load for the night-fighter Tigercat in Korea was a single external fuel tank hung on the centerline station, two 1000 pound general purpose bombs or two napalm bombs hung on inboard wing stations, and eight 5 inch HVAR rockets mounted on the outboard rocket stations.  This gave the Tigercat the best combination of performance, ordnance, and loiter time in order to perform the night fighter mission.[11]

            Unlike the F4U-5N, the F7F-3N and 4N did not have a dedicated night gunsight.  The Tigercat carried the Mk-8 gunsight which was the standard for day fighters of the time.  It had gyro-scopic range controls which enabled the pilot to fire accurately at airborne targets, but it did not have any adjustable functionality for air to ground bombing.[12]  Unlike the Mk-20, it did have a setting for rocket and gun air to ground attacks.  By setting the sight to “fixed”, selecting either gun or HVAR, and the dive angle switch to above 35 degree or below 35 degree, the pilot would get rudimentary symbology to aim the guns or rockets.[13]  The Mk-8 was adjustable for night use, but it was not built for that purpose.  In order to use the sight at night the pilots would turn down the Mk-8 to a barely visible setting that would enable them to see airborne and ground targets through the gunsight.  If the setting was set too bright, the pilot would lose the target once it was brought into the gun-sight range rings.  For bombing attacks, the pilot had to rely on instinct, experience, and an interpretation of where the target was in relation to dive angle, airspeed, altitude, and ordnance selected on the gunsight.[14]  

SCR-720 characteristics and operation

The SCR-720 was the most widely used airborne Intercept radar of World War II.  It outfitted the P-61 Black Widow, the British Beaufighter, and the Mosquito to name a few aircraft.  The SCR-720 was a pulse radar with parabolic dish that rotated 360 degrees around its vertical axis.  The aft 210 degrees was blanked off due to the radar scanning into the aircraft body.  The radar dish would also rotate slightly in the horizontal axis to provide altitude coverage.  The dish rotated at 360 revolutions per minute and the radar weighed 412 pounds.  The SCR-720’s azimuth accuracy was plus or minus 3 degrees and the elevation accuracy was plus or minus 2 degrees.  Its elevation limits were -10 degrees to + 65 degrees off the aircrafts attitude.[15]

The RO was provided with two rectangle shaped scopes with the SCR-720.  A “B” scope which provided azimuth and range and a “C” scope which provided elevation and azimuth.[16]  The “B” scope was selectable to 120nm for beacon and ground mapping operations, and 20 nm, 10 nm, and 5 nm ranges for airborne intercepts.  A “C” scope gave elevation difference compared to the attitude of the night fighter.  Unlike the APS-19, the RO had to adjust gain and radar tune functions which helped break out the radar contact and radar signals when compared to other radar returns.  The RO also controlled the tilt of the radar with SCR-720 which enabled it to search for and track targets above the aircraft.  The “B” and “C” scope setup was more intuitive that APS-19’s “H” scope setup, but the SCR-720 was much more user intensive and could not have been used without a dedicated RO.[17]  

            The SCR-720 did provide rudimentary ground mapping but the small rectangle “B” scope would warp the picture.  F7F-3N RO’s claim the radar was only good for mapping significant terrain features, like a shoreline.[18]  The beacon function worked similar to the APS-19 with beacon radar return being received out to the “B” scope limits of 120nm.  The RO would also have to interpret changes in azimuth and range in order to estimate the targets heading and velocity.  The SCR-720 had a maximum detection range of 18 miles on a large airborne target though 5 to 7 miles was the norm for a metal skinned fighter sized target. Though the SCR-720 was significantly older than the APS-19 when the Korean War started, many RO’s regarded the SCR-720 as the better radar.  This could be in no small part to the fact that the RO’s trained on the 720 after World War II and it did not have the automatic features of the APS-19.  Additionally, RO’s felt some professional job satisfaction at being able to operate the SCR-720 well and direct the pilot to a successful night intercept.[19]

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(Appendix 5 – SCR-720 airborne Intercept interpretation.)

F4U-5N and F7F-3N/4N tactics

The F4U-5N and the F7F-3N and 4N served in Korea during the same time period.  VMF(N)-513 flew F4U-5Ns and F7F-3Ns out of Japan during the early days of the conflict. While VMF(N)-542 brought F7F-3Ns from the United States a few months later.  Eventually VMF(N)-513 would relieve VMF(N)-542 on the Korean Peninsula operating out of Pusan East (K-9 airfield).  VMF(N)-513 became a large squadron operating F4U-5Ns, F4U-5NLs, F4U-5s, and F7F-3Ns.[20]  The Marine Pilots were interchangeable, flying day and night Corsair and Tigercat missions.  Since the same pilots flew the Tigercat and the Corsair, and the aircraft’s weapons, capabilities, and radar performance were similar, the tactics, both air to air and air to ground were, for all intents and purposes, the same.

Airborne Intercept

The Corsair and Tigercat night fighters were heavily dependant on Ground Control Intercept (GCI) controllers located with the Tactical Air Direction Center (TADC).  The Night fighters would operate as single aircraft over a pre-determined combat air patrol (CAP) locations.[21]  The pilots and the RO’s would brief with intelligence and operations before the flight.  They would receive mission information including flight and GCI callsigns, takeoff time, on-station time, CAP location, expected threats, and GCI radio frequencies.  The aircraft would takeoff at their appointed times and fly to their designated CAP positions.  The radars at the TADC would pick up airborne targets at ranges over 100nm depending on altitude of the target.  Using the identification features of their ground-based radar, GCI could determine if the contact was emitting friendly transponder codes.  If the radar site was able to track the contact from enemy territory and it did not have a friendly transponder code, the senior officers at the TADC could declare the contract as a “bandit”, which was a code word for a know enemy aircraft.  If a radar contact was not a known enemy or friendly aircraft, it would be declared a “bogey”.  (Bandit and Bogey are still used today.)[22]   After the radar contact was declared “bogey”, or a “bandit”, the TADC would then determine the friendly CAP aircraft that was in the best position to intercept the contact.  The aircraft would be directed to contact a specific GCI controller on a specific frequency.  The GCI controller and the crew of the aircraft would then work as a team to make the intercept.  Since the SCR-720 and the APS-19 had short ranges and did not display heading accurately, the GCI controller would vector the fighter around in order for the fighter to intercept the radar contact from the rear hemisphere.  If the fighter came at the radar contact from the forward hemisphere, the short acquisition range of the night fighter radars would make a successful intercept by the fighter very difficult.  

(A fighter flying at 200 kts, outfitted with an SCR-720 or an APS-19 radar could theoretically offset 70 degrees at 5nm, maintain radar contact, and execute a stern conversion on a radar contact that was also flying at 200 kts.  This would take an exceptional radar operator and pilot.)[23]   

 The GCI controller would vector the aircraft by giving it headings to turn to.  It would also give the fighter the position of the radar contact in relation to the fighter’s nose in order for the fighter’s radar to pick up the contact.  Once the fighter’s airborne radar picked up the radar contact, control would shift to the fighter aircrew to consummate the intercept.  The GCI controller would continue to monitor the intercept in case the fighter lost radar contact.[24]

            The pilot of the F4U-5N or the RO of the Tigercat would gain a radar contact.  By monitoring the radar, the fighter would fly into a position in order to make a visual identification of a “bogey” contact or to shoot down a “bandit” contact.[25]  The pilot or the RO would monitor closure and changes in azimuth in order to close on the target in a controlled fashion.  If the intercept was flown recklessly, the fighter could be flown outside of radar parameters or worse, the fighter could fly out in front of the enemy aircraft.  Intercepts could take several minutes from first radar contact to close to a visual identification.  Patience was important for the Korean Night fighter aircrew.  

            The RO of the Tigercat would direct the pilot by giving him a heading and altitude to fly to.  “Turn right to 320 and climb to angels 21” would be a call the RO would make and it would direct the pilot to turn to a heading of 320 degrees and climb to 21000 feet.[26] The pilot of the Tigercat only had a small repeater of the “B” scope in the front cockpit and this did not offer enough information for the pilot to make an intercept.[27]  It was a team effort in the Tigercat for an intercept to occur.  The RO would also call out azimuth and distance to the target in order for the pilot to make visual contact.  “1 o’clock at 4000 feet”.  Once the pilot visually acquired the target he would call “tally” over the intercom and he would finish the intercept visually.  

Once the pilot visually acquired a “bogey” target, the pilot would close slowly on the target aircraft in order to visually identify it.  On dark nights the fighter might need to close to within a few feet of the aircraft to identify it.  Once the identification was made, he would relay the information back to GCI and that target would now be identified as an enemy (“bandit”).[28]  The fighter would separate from the enemy aircraft by slowing or by using turns away to provide separation from the target.  The fighter would then try to gain a couple hundred yards of separation and then place the enemy aircraft in its gun sight.  The fighter could then open up on the aircraft.  

            If the radar contact was declared a “bandit” at the beginning of the intercept, the fighter could forego the hazardous identification portion of the intercept and close to 20 mm cannon parameters, 500 to 1,500 feet, and open fire. 

While it was possible for the F7F-3N and the F4U-5N to shoot down enemy contacts without visually acquiring them by using the gun aim function of the radar, they did not use this function during the Korean War.[29]  The Marine Corps night fighters would have to wait for a more advanced radar fighter to be introduced to get a non-visual kill.  During the Korean War, Marine Corps F4U-5Ns and F7F-3Ns achieved two night air to air confirmed kills each. The first by an F7F occurred in June of 1951.

Late on the night of 30 June 1951, Capt. E.B. Long and Warrant Officer R.B. Buckingham lifted their F7F-3N Tigercat off for a night combat air patrol (NCAP). Throughout the month other VMF(N)-513 aircraft had registered fleeting radar contact with slow, low-flying aircraft, but these contacts had quickly faded. By 2240, the F7F-3N was on station and waiting word from the TADC (tactical air direction center) “DENTIST”. This was a ground radar installation located in southwestern Korea that searched the night sky for enemy aircraft. At 0100 “DENTIST” contacted Long and Buckingham with intercept vectors for an unidentified contact flying north of UN airfield K-14. Buckingham, in the backseat of the F7F-3N, established contact with the target at a range of 5,000 feet on the plane’s SCR-720 radar and directed Long toward the unknown plane. Long then recognized the aircraft as a PO-2 (NATO Code named “Mule”). The PO-2 was apparently on a night heckler mission and flying at an altitude of 3,500 feet at a airspeed of only 80 knots. Long positioned his aircraft behind the PO-2, but since the F7F-3N was flying at nearly 200 knots, Long quickly overtook the slower airplane. Maintaining visual contact with the PO-2, Long brought the Tigercat around for another pass and did everything he could to slow the big plane down. He dropped full flaps, the landing gear, and started steep “S” turns to bring his airspeed down to 95 knots, just over the F7F-3Ns stall speed.  At this slow speed, Long made three firing passes at the PO-2, one from directly behind the plane and two from the right. On each pass, Long fired roughly 50 rounds of 20mm ammunition at the ghostly biplane. The observer in the backseat fired his hand-held light machine gun in defense of his tiny aircraft. After the third pass, Long and Buckingham watched the PO-2 crash into the banks of the Han River near Seoul. “DENTIST” had reported that the bogie had disappeared from his scopes. Long reported an explosion and fire where the plane had hit the ground. The VMF(N)-513 had its first confirmed night kill.[30]

From the cocaine, blood and flying scarves of World War One dogfighting to the dark arts of modern air combat, here is an enthralling ode to these brutally exciting killing machines.

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APPENDIX 4

F7F-3N Tigercat                                            kalaniosullivan.com

F7F-3N Radar Operator station.                                        http://www.chinalakealumni.org

F7F-3N Pilot Instrument Panel.                              uscockpits.com

F7F-3N Radar Operator Panel.

APPENDIX 5


[1] Miska, Kurt, Air Combat Special, “Tigercat”(Rockaway, N.J.: Eagle Aviation Enterprises, 1971) 6.

[2] Doll, Thomas E., Night Wings, USMC Night Fighters, 1942-1953 (Carrollton, TX: Squadron/Signal Publications, INC. 2000) 49.

[3] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-1N, F7F-2N, F7F-3, F7F-3N, F7F-4N Airplanes (Washington D.C. 1947) 1.

[4] Condon, Corsairs to Panthers, 3.

[5] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-3N, 1.

[6] Scarborough, W.E., F7F Tigercat in Action (Carrollton, TX, Squadron/Signal Publications, Inc. 1986) 44.

[7] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-3N, 1.

[8] Scarborough, 19.

[9] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-3N, 1.

[10] Miska, 27.

[11] Various Email interviews with former F7F-3N / 4N aircrew.

[12] Email interview with Bob Dahlberg, Col, USMC (ret).  F4U-5N/F7F-3N pilot, VMF(N)-513, 29 May, 2008.

[13] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-3N, 49.

[14] Email Interview with Lynn Williams, Major USMC (ret) VMF(N)-513,1951, August 14, 2008.

[15] AI MK-10 Aircraft Intercept Radar; available online: http://website.lineone.net/~norman.groom/AI_MKX.htm, accessed 16 May, 2008.

[16] Stimson, George W., Introduction to Airborne Radar, 2nd Ed. (Medlam, NJ: SciTech Publishing, Inc. 1998) 21.

[17] Bureau of Aeronautics, Pilot’s Handbook for Navy Model F7F-3N, 49.

[18] Interview with Eugene Holmberg, VMF(N)-513 RO 1951-1953, conducted 12 May,2008.

[19] Various email interviews with F7F-3N aircrew.

[20] Doll, 56.

[21] “Night Hecklers over Korea” declassified Naval Aviation News article from August 1952.

[23] Intercepts performed via simulator by author with target airspeed ranging from 90 miles per hour to 220 miles per hour and fighter airspeeds ranging from 150 miles per hour to 250 miles per hour. Executed 70 degree offset at 5 nm and maintained offset until stern conversion completed. 

[24] Kunsan Airbase, VMF(N)-513 “Flying Nightmares” (1951-1954) , 19 June 2001, available from http://kalaniosullivan.com/KunsanAB/VMF513/Howitwasa1ac.html#Corsair; internet; accessed 22 August, 2008.

[25] Doll, 67.

[26] White, J.G., “Cherry Point Corps’ AIO Training Center”, Cherry Point Windsock, July, 3, 1953, 5.

[27] Miska, 14.

[28] Email interview with Bob Dahlberg, Col, USMC (ret).  F4U-5N/F7F-3N pilot, VMF(N)-513, 29 May, 2008.

[29] Bureau of Aeronautics, Operation Instructions Radar Set AN/APS-19B, 19.