LOOKING BACK Model 690

The Model 690 was the twenty-first to be placed into production, all by the Aero Commander Division of North American Rockwell Corporation at Bethany (Wiley Post Airport), Oklahoma City, Oklahoma.

The 79 examples were built between February 1969 and September 1973, serial numbers 11000 through 11079, although serial number 11070 was not built. Of these, two were initially certified in 1969; 1 in 1970; 1 in 1971; 48 in 1972; 26 in 1973; and 1 in 1974. A factory document describes the Model 690 as “Certified July 19, 1971. Similar to Model 681. Changes include: a) Gross weight increase to 9,850 lbs.; b) wing length increased 30 inches at center wing section; c) AiResearch TPE331-5-251K engines; d) increased rudder area; and e) increased baggage capacity to 600 lbs.” The Model 690 was indeed certified on July 19, 1971, under Type Certificate 2A4 and had AiResearch TPE331-5-251K engines, although the first three examples, respectively, originally had TPE331-1-151, TPE331-02-201 and “TPE331-5-251.”

The original propellers were 4-blade, 90-inch-diameter Hartzell HC-B4TN-5C/T10178-14 for the first example; the 3-blade, 90-inch-diameter Hamilton Standard 33LF-325/1033A-0 for the second; the 106-inch-diameter Hartzell HC-B3TN-5DL (with either LT10282A+4 or LT10282AB+4 blades) for the third; and the 106-inch-diameter Hartzell HC-B3TN-5FL/LT10282H+4 for the fourth. The last 75 examples had the 106-inch-diameter Hartzell HC-B3TN-5FL/LT10282HB+4. TPE331-5-252K engines can be installed under STC No. SA1024SO.

Gross weight was increased to 9,850 pounds on the prototype but was subsequently increased to 10,250 pounds. Cabin pressure differential is 4.2 psi giving a 13,000-ft cabin at 27,955 feet and a sea level cabin at 9,025 feet.

The 690 was the first Turbo Commander to have a rudder trim tab that was of a taller span (height) and shorter chord than previous models. But the major change to the design was to locate the nacelles 15 inches further away from the fuselage in order to reduce cabin noise. This was achieved by a 30-inch stretch of the wing at the centerline. This moved the point at which the dihedral started to 15 inches outboard of the fuselage.

As is the case with all Commanders, all spars and stringers were continuous at the centerline with all splices outboard of the nacelles. The TPE331-5 series engine, which was then available, had undergone a gearing change resulting in a propeller speed reduction from 2,000 rpm to only 1,591 rpm. This required the propeller diameter increase to 106 inches, although the tip clearance with the side of the fuselage did increase from 7.5 inches to 14 inches. Vmc considerations because of horsepower and the nacelle location necessitated an improvement in rudder power. As a weight reduction consideration, the new rudder utilized a horn balance instead of the less-efficient leading-edge balance weights used in all previous Commander rudders.

The 690 was the first Commander model to incorporate electric aileron trim. The trim tab was added to the left aileron and driven by an electrical actuator. This tab was also balanced with a “lollypop” type weight. In August 1971 serial number 11003, N9203N, was flown to the U.K. for evaluation by the Royal Air Force for a requirement in a multiengine training role. It was not successful, however, and the Handley Page HP.137 Jetstream was selected instead, probably as a result of a “buy British” policy. Some 26 were ordered as the Jetstream T.1.

On April 7, 1972 serial number 11007, N9207N, flown by James L. Badgett, who at the time was President of Schick Enterprises Inc, established three world records in FAI Class C1e, Group II for turboprop aircraft in the 3,000 – 5,999 kg (6,614 – 13,225 lb.) weight category. The first record was established for “speed over a closed circuit of 500 km without payload” of 543.36 km/hr (which equates to 293.4 kts or 337.63 mph); the second was a straight-and-level speed record of 609.09km/hr (which equates to 328.9 kts or 378.47 mph); while the third was for altitude in horizontal flight, reaching 10,625 meters (34,859 ft).

Barry Collman’s lifelong interest in airplanes began when he was growing up in a house located underneath the downwind leg to busy Northolt aerodrome, an R.A.F. base near London-Heathrow airport. As a young teenager he discovered airplane “spotting”–hobbyists’ observation and logging of aircraft by make, model, and registration number. The hobby began to grow into a passion as Collman joined a club of like-minded spotters. At one point he purchased a copy of the January 1966 U.S. Civil Aircraft Register, and thumbing through it came upon the Aero Commander. He was hooked. Eventually he acquired every available FAA microfiche file on Commanders, and since 1995 has made annual pilgrimages to Oklahoma City to sift through FAA records. He now has a database with about 100,000 records as well as a collection of negatives, slides, photographs, digital images, magazines, brochures, knick-knacks–and a very understanding wife. This series on Commander production history originally was written for the Twin Commander Flight Group, of which he is an enthusiastic member.

Scanned from an image taken by an unknown photographer, the photo depicts N9206N, serial number 11006, at Washington Dulles international Airport on May 26, 1972. This was no doubt at an official event. It is finished in factory paint design “3M Waikiki Blue,” the colors being Off White, Electric Blue and Shadow Blue. Certificated on February 19, 1972, it was registered to Aero Commander Division, North American Rockwell Corporation on March 8, 1972, and retained for use as a demonstrator. It was subsequently registered as N1JW, N15JW, N150W, N515AR, N690SP, HZ-SS1 (Saudi Arabia), ZK-MOH (New Zealand) and finally N71AH. Currently registered to Sky West Aviation Inc (Trustee), of Albuquerque, New Mexico, it is thought to be operated by GeoFly GmbH., of Magdeburg, Saxony-Anhalt, in Germany.