Otter 151 was delivered to the United States Navy on 28th September 1956 with BuAer serial 144670. On that day the Otter was flown by a Navy pilot from Downsview to Griffiss Air Force Base, New York State, where it overnighted. The Otter completed its delivery flight the following day, flying from Griffiss to the Naval Air Station at Quonset Point, Rhode Island, home base of VX-6 Squadron. This Otter was one of a batch of six delivered to VX-6 during September/October '56. All six were transported to the Antarctic, some by ship and some on board USAF Douglas C-124 Globemasters.
144670 remained with VX-6 for the entire period the Squadron operated the Otter in the Antarctic, although it was occasionally transported to New Zealand for maintenance and local use there. During one such visit it was involved in a landing accident at Ashburton Airfield, South Canterbury, to the south of Christchurch, New Zealand, on 3rd December 1961. The Otter was attempting a cross-wind landing, in the course of which the undercarriage collapsed and the propeller was bent. The Otter was backloaded to the United States for repairs and then returned to Antarctica. 144670 also made a forced landing on the Skelton Glacier after an engine failure on 6th January 1965. There were no injuries or damage and the engine was changed at the site. It continued in use until January 1966, and took the honour of making the Navy's last Otter flight in the Antarctic on 23rd January 1966, a two hour sortie from and back to McMurdo. It had flown a total of 533 hours in Naval service up to that point. It was transported back to the United States and on 1st October 1966 was assigned to the Naval Test Pilot's School (NTPS) at Patuxent River Naval Air Station, Maryland where it has served ever since.
In the course of the aircraft's long Naval career, only one other incident is recorded, which occurred on 20th October 1981, by which stage the Otter had accumulated 3,500 hours total time. On the day in question, 144670 was being flown by a Royal Navy exchange pilot and was en route from Patuxent River to the nearby auxiliary airstrip at Webster Field on a training detail. The engine quit half way across the St. Mary's River, as a result of a massive fracture/failure of the number nine cylinder head. The pilot turned back and glided towards a field for a forced landing. The landing was successful but the field was none too big and with the Otter fast approaching a stand of trees, heavy breaking was required. The aircraft came to a halt just before reaching the trees, but tipped over on its nose and then fell back heavily, badly damaging the rear fuselage. With its wings removed, 144670 was towed back to Patuxent River NAS., behind a pick-up truck, making an ignominious entrance through the main gate in this damaged condition. It languished in the back of the NTPS hangar until a new rear fuselage section arrived, when it was repaired. It was back flying as an active member of the NTPS fleet by March 1982.
The function of the NTPS is to train test pilots for the Navy, Marines and Army, as well as contractor test pilots who will be working on aircraft intended for military service. Although most of the students are US personnel, the School also accepts exchange pilots from other services and British, Italian etc pilots have attended the School's courses. The NTPS has 36 aircraft of eleven different types. These range from gliders to helicopters, multi-engined aircraft and fast jets. The students on the course will fly all of these aircraft types, to expose them to the complete range of flying experience. Some of the graduates of the School remain test pilots; others return to operational units, bringing their experience with them. The NTPS has three instructor pilots qualified on the Otter.
With the NTPS, Otter 144670 is designated as an NU-1B, the 'N' prefix denoting that the aircraft is assigned to special test duties. NTPS documentation describes the Otter as “A low speed, side-byside, medium weight, tail wheel configured, propeller-driven aircraft which exhibits unusual STOL characteristics”. Apparently the Otter is an essential part of the NTPS fleet, as it has been for nearly forty years, because of the adverse flight characteristics it possesses! Its “colourful flying qualities” are much prized by the School's instructors. These include the fact that it has to be hand flown, or will tend to diverge into an unstable spiral mode, and the adverse yaw it demonstrates in a turn, requiring constant control inputs.
Flying the Otter exposes the students to an aircraft type they will not be familiar with, which many find quite a handful, and will demonstrate their personal limitations. Flying a fast jet, such as the F-18 Hornet, is by all accounts a simple matter compared with trying to assert mastery over the Otter. Over the years there have been quite a few excursions off the runway into the grass, aileron drags on take-off, and occasionally a few inches shaved off the propeller when it has made contact with the concrete, and all this by the Navy's finest. Little wonder 144670 is known as “The Humbler”. With about fifty pilots a year flying the Otter, there must be many interesting reminiscences when Naval aviators meet as to their treatment at the hands of The Humbler.
A visit to Patuxent River NAS in April 1998 saw 144670 (at that stage with 6,566 hours on the airframe) sitting majestically on the NTPS ramp, looking somewhat ancient in comparison with the other occupants of the ramp, T-38s, F-18s etc. It was in an all white scheme with red trim and carried fleet number 30. Inside, it still retained the JATO panel and switches from its days in the Antarctic with VX-6. Another reminder of that era is the celestial navigation fitting for the periscopic sextant. Internally, it has an 'elevator position indicator', used so that the student will know the position of the elevator during various manoeuvres. Externally the Otter has a test instrumentation probe on the starboard wing, used to measure the side slip angle and angle of attack. In all other respects it is a standard Otter.
The NTPS also has two U-6A Beavers on strength. These are used for 'adverse handling' demonstrations and for towing the School's gliders. The manufacturer no longer supports the Beaver or the Otter, but the School has its own mechanics who are qualified on the aircraft, and parts are obtained from such suppliers as Newcal Aviation of New Jersey or Viking Air of Vancouver. Originally the Otter was maintained at Pensacola NAS, Florida but since 1979 all maintenance has been carried out at Patuxent River. At one stage a request was made for funding to purchase floats for the Otter, but was vetoed on cost grounds.
Also based at Patuxent River is the Naval Air Test Centre and there are many restricted areas in the vicinity where the NTPS and NATC aircraft can carry out their flying. A typical mission with the Otter will see it take off from its Patuxent River NAS base and proceed to the North West Sector, bounded by Chesapeake Bay and the Potomac River, south of two power stations. Here, handling trials will be carried out, demonstrating longitudinal stability and control and lateral directional stability. While entering the area “TESTER 30”, the Otter's radio callsign, will announce its intentions on UHF to ensure clearance from the Beavers and any NTPS helicopters which may also be using the sector. As the circuit at Patuxent River is not suitable for the slow-moving Otter, given the amount of fast jet traffic at the base, Webster Field some eight miles from Patuxent River is used. After the handling trials in the north-west sector are complete, TESTER 30 will proceed to Webster Field for landings, touch-and-goes etc to demonstrate to the student its STOL flying qualities. The mission will then conclude with a return to base, where the student will assess and describe what he has experienced.
144670 is the world's last serving military Otter and by August 2001 had 6,900 hours on the airframe. It was still active during 2011 and expected to remain in service for many more years.
Full history courtesy of Karl E. Hayes © from DHC-3 Otter: A History (2005).