The Model 690C, marketed as the JetProp 840, was the twenty-fifth type to be placed into production, the first 63 by the General Aviation Division of Rockwell International Corporation at Bethany (Wiley Post Airport), Oklahoma City, Oklahoma; the next 52 by Gulfstream American Corporation, Commander Division; the penultimate one by Gulfstream Aerospace Corporation, Commander Division; and the last one of this model by Gulfstream Aerospace Corporation, Oklahoma Operations.
The 122 examples were built between May 1979 and May 1985, serial numbers 11600 through 11703; 11709; and 11719 through 11735.
Of these, 16 were initially certified in 1979, 41 in 1980, 48 in 1981, 10 in 1982, 3 in 1983, 3 in 1984, and 1 in 1985.
A factory document describes the Model 690C as “Certified September 7, 1979. Similar to the 690B, but several changes were made. The most notable changes were: a) 30-inch wing tip extensions added; b) increased seating from 10 to 11; c) Zero fuel weight reduced from 8750 to 8463 lb.; d) AiResearch TPE331-5-254K engines; e) Dowty Rotol propellers; f) engines canted down 2 degrees; g) wet wing outboard of the nacelles added; h) fuel capacity increased from 384 to 425 gallons; i) nacelles redesigned; j) landing/recognition lights were added to the nose; k) extended baggage compartment floor; and l) canted wing tips added.”
The model 690C was indeed certified on September 7, 1979, under Type Certificate 2A4 and had AiResearch TPE331-5-254K engines. The first example had the 106-inch diameter Dowty Rotol (c)R.305/3-82-F/8 ‘”supercritical” propellers (blade model not known), while the next 114 used the (c)R.306/3-82-F/7 / VP2926 (with a B.F. Goodrich de-icing kit), and the last seven the (c)R.306/3-82-F/7 / VP3027 (with Dowty Rotol de-icing boots). The Dowty Rotol propeller had a supercritical-type blade form whereby the blades selected for a particular propeller assembly were not only matched in weight but also in centroid. This made for very smooth-running propellers. While performing propeller strain gauging flight tests in Bethany the Dowty Rotol technician made the comment that a slight downward tilt of the engine installation would position the propeller disk more perpendicular to the airstream, thus resulting in smoother operation as well as longer propeller life.
TPE331-10T “Dash Ten” series engines are available for installation under STC No. SA236CH.
Gross weight is 10,325 pounds and the cabin pressure differential is 5.2psi, giving a 13,000-foot cabin at 33,059 feet and a sea-level cabin at 11,595 feet.
Although the cabin pressure remained at 5.2 psi, same as the 690B, a new direct-bleed environmental system was incorporated. This system had been designed for the pressurization increase planned for the new model 695A/690D fuselage. It was utilized on the 690C to take advantage of a 60-pound weight saving over the old multiple jet-pump system used in the 690B.
Total fuel capacity is 430 U.S. gallons (1,628 litres) as standard, with an optional capacity of 482 U.S. gallons (1,825 litres). Two complete and independent fuel systems were created. This was the first time a Commander deviated from the single-tank concept. The center fuselage sump was replaced with a sump and fuel pick-up area in each system, just outboard of the fuselage and forward of the rear spar. The submerged-type boost pumps used on all previous Commanders were now replaced by inline-type boost pumps located in the nacelles. Each fuel system supplied its respective engine. An interconnect valve (normally closed) in a centerline wing bulkhead allowed fuel to flow by gravity from one system to the other in a single-engine or fuel-imbalance situation. The increase in usable fuel quantity to 474 gallons involved the following:
One additional flexible fuel cell was added in each system outboard of the MLG wheel well and forward of the rear spar. The entire wing torque box outboard of the nacelle (including wing panel extensions) was redesigned as an integral fuel tank. All fuel inboard of the nacelles remained in flexible cells. A single fuel port for each system was located outboard of the nacelle in the wet wing area. This combined with an increased number of enlarged interconnect tubes across the nacelle area made a great improvement in fuelling time. Marketing literature says 474 gallons could be now be put aboard in 20 minutes.
The Model 690C was the first of those marketed as the “JetProp” series and had a longer wingspan, with 32-inch panels added outboard of the ailerons and “winglets” giving an increase in total span to 625.47 inches. The landing lights were re-positioned back to the nose, as preferred by pilots, who had commented that the extension speed limits on the retractable wing-mounted lights precluded their use as recognition lights on high-speed let-downs.
From serial number 11719, the Model 690C also featured a cosmetic dorsal fillet, but this time it was a much shorter one that started higher up the fin.
On March 25, 2004, serial number 11640, registered as N840KB, was issued a Certificate of Airworthiness in the Experimental – To Show Compliance category, for collection of performance data applicable to the FAR requirement of RVSM (Reduced Vertical Separation Minimum). This reduces the vertical separation between Flight Levels 290 to 410 from 2,000 feet to 1,000 feet and thereby makes six additional flight levels available for operation.
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.
A digital image taken by Jarrod Wilkening on February 25, 2017 at Houston- David Wayne Hooks Memorial Airport, Texas, N777NV is serial number 11680. Originally Certificated on June 19, 1981 it was exported to Distributor, Commander Jetprop de Venezolana, in Caracas, Venezuela as YV-415CP, for SA Construcciones y Parcelamientos (SACONPA), of Valera, which is in the State of Trujillo. In December 1988 it returned to the United States as N7052J and after a spell in Mexico as XA-JYNM, became N680WA in December 1996, then N777NV on February 9, 1998 with the State of Nevada, Department of Transportation, in Carson City. As clearly evidenced in the image, a Zeiss RMK aerial survey camera was installed in January 1998, together with photographic glass in the emergency exit window. At the same time, the standard TPE331-5-254K engines were replaced by TPE331-10T-511K, with Hartzell “Q-tip” propellers. In April 2020, new registration marks were assigned, being N885LV.
Top photo of 690C, N5871K
Scanned from a slide taken by Mike Madden in March 1980, shortly after arrival at Moorabbin Airport, Victoria, Australia. N5871K is serial number 11619 and was finished in factory paint design #Standard, in Bavarian Cream, Condor Gold Metallic and Medium Bronze Metallic. Certificated on February 8, 1980, and having had an Export Certificate issued on the same day, it was sold to the Australian Distributor, Civil Flying Services Pty Ltd and then registered in Australia as VH-UVT on October 16, 1980. Ownership having been transferred a couple of times. It was exported back to the United States and became N16TG on July 6, 1990. After having been re-registered as N86ST in October 1992, it became N72TB in December 1992 and is currently registered as such. Note the nose lights and the absence of a dorsal fillet, a feature that was not incorporated until serial number 11719.
