Info on Model 685, G-BFGB at end of article The Model 685 was the twenty-second type to be placed into production, the first 43 by the Aero Commander Division of North American Rockwell Corporation at Bethany (Wiley Post Airport), Oklahoma City, Oklahoma; the next 21 by the Commander Aircraft Division of Rockwell International Corporation; and the last 3 by the General Aviation Division of Rockwell International Corporation. It was the last of the “Speedline” nacelle piston models.
The 67 examples were built between February 1970 and May 1975, serial numbers 12000 through 12066. Of these, one was initially certified in 1970; 17 in 1972; 36 in 1973; 11 in 1974; and 2 in 1975.
A factory document describes the Model 685 as “Certified September 17, 1971. Similar to 690. Primary difference is the 685 is a piston-powered aircraft, using two Continental GTSIO-520 engines with non-reversing Hartzell propellers. Gross weight was decreased to 9,000 lbs.”
The Model 685 was indeed certified on September 17, 1971, under Type Certificate 2A4 and the first example had the engines quoted as just “Continental GTSIO-520.” The following 37 had the 435 horsepower Continental GTSIO-520-F, while the last 29 had the Continental GTSIO-520-F1B. However, under a factory program, the “F” series engines were changed to -K or -K1B variants, as it wasn’t long before the factory started to receive reports of engine failures. It was discovered that the problem initiated with ring flutter, followed eventually by a piston burn-through and terminating in over-pressurization of the crankcase. This forced all of the lubricating oil overboard through the propeller shaft seal. A rather lengthy investigation by Aero Commander and Continental led to a number of changes including flight manual and winterization procedures to minimize engine overcooling; improved cylinder and cowl baffling; engine redesign resulting in certification of the “K” series engine; and replacement of all “F” series engines.
The first two Model 685 Commanders used different Hartzell propellers initially, respectively the 88-inch diameter HC-E3YF-2A/C8475+2 and the 88-inch diameter HC-H3YN-2/C8475+2. The next 52 had the HC-H3YN-2F/FC8475+2 variant and the remaining 13 the HC-H3YN-2F/FC8475B+2.
Gross weight is 9,000 pounds and the cabin pressure differential is 4.2 psi, giving a 13,000-foot cabin at 27,955 feet and a sea level cabin at 9,025 feet. The system was the same as the Model 690 except that it drew its bleed air from the engine turbocharging compressor that was powered by an exhaust driven turbine.
The Model 685 is visually identified by the combination of cockpit overhead or “eyebrow” windows, a squared vertical fin cap, and a rudder horn balance.
Model 685, s/n 12032, VH-NJT Taken on July 14, 2016 at RAAF Base Tindall, near Katherine, Northwest Territory, Australia by Russell Legg, VH-NJT is serial number 12032. Originally certificated on May 21, 1973 as N9199N, it was sold to Walter Ives, of Jannali, New South Wales, Australia and registered there as VH-NJT on January 23, 2014.
Early in the design of the Model 685 engine installation it was found that the propeller plane location was not compatible with the picture window configuration of the 690 fuselage. The Turbo Commander propeller plane falls further aft on the fuselage. Thus, the fuselage had a small window immediately aft of the door and a wide skin panel between that small window and the picture window. This skin panel is intersected by the Turbo Commander propeller plane and formed an ice shield. The Model 685 propeller plane fell further forward and thus would have fallen across the small forward window noted above. This dictated a redesign for the 685, which placed the skin panel/ice-shield area immediately aft of the door and created three smaller windows aft of that panel. This redesign proved to be a blessing in disguise because of the cabin noise attributed to the large area of glass in the picture window and the weight of the structure surrounding that large opening.
The Model 690 wing stretch placed the 685 propeller arc 23.5 inches from the side of the fuselage. This, combined with the smaller windows and the over-wing exhausts, gives the 685 perhaps the quietest interior of any Commander.
On January 23, 1973, serial number 12003, N165SE, flown by the President of Schick Inc., James L. Badgett, established two world records. The first was for an altitude of 35,450 feet (10,805 meters), and the second was for an altitude maintained at a constant speed, being at 35,000 feet (10,668 meters).
On January 2, 1974, serial number 12049 was converted to a Model 685A and given a new serial number: 12100. It was then converted back to a Model 685, as serial number 12049, in February 1977.
The 685A initially used the 435 horsepower GTSIO-520-F1B engine with the 88-inch diameter Hartzell HC-H3YN-2F/FC8475+2 propeller and later used the GTSIO-520-K1B with the 94-inch diameter HC-H3YN-5F/FC9684-4.
Gross weight was 9,200 pounds and the cabin pressure differential was 5.2 psi, giving a 13,000-foot cabin at 33,059 feet and a sea level cabin at 11,595 feet.
The 685A had electrically heated windshields, the same as 690A; electric aileron trim, same as the 690; a revised fuel system with new gaging; a nacelle fire warning system; and a new brake installation.
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.
Taken on April 9, 1979 at Coventry-Baginton Airport, UK by Bob Hodgkins, G-BFGB is serial number 12049. Originally built as a Model 685 N5071E, it was converted to the sole example of a Model 685A and re-serialled 12100, in January 1974. The proposed Model 685A was not proceeded with however and it was converted back to a 685, as s/n 12049 again, in February 1977. In December 1977, N5071E was cancelled on export to the UK, where it became G-BFGB and was sold by Distributor, Glos-Air Ltd., of Bournemouth-Hurn Airport, Dorset, to the British Airports Authority plc, based at London-Gatwick Airport, West Sussex. The high-viz scheme undoubtedly reflects operations in and around busy airports, checking nav-aids and ILS systems etc. Underneath the wing is a camera pod that was installed in March, 1978. It returned to the USA in July 1981, as N808AC but later, as N60QR, it was used as the test-bed aircraft for the Orenda OE600A water-cooled engine. Its current status is uncertain, as registration expired on October 3, 2016 and was subsequently cancelled on March 14, 2018.
