Teledyne-Ryan Compass Cope YQM-98A R-Tern

By: John C. Evans

USAF Compass Cope RPV Program Objectives

-    High Altitude Long Endurance Flight over 55,000 Feet MSL & 24 Hours

-    Vehicle System Redundancy

-    Capable of Takeoffs and Landings from Improved Runways

Boeing GQM-94 B-Gull Compass Cope RPV

    (Original single source supplier of the USAF Compass Cope-R Program)

In 1971 Military and Intelligence Communities formulated a requirement for a high-altitude long-endurance RPV (Remote Piloted Vehicle).  The Compass Cope program was initiated by the USAF to develop an upgraded intelligence drone that could takeoff and land from improved runways like a manned aircraft, and operate at altitudes above 55,000 feet MSL for up to 24 hours to perform surveillance, communications relay, or atmospheric sampling.  A single source contract was issued to Boeing & General Electric to design, build, and test two RPV technology demonstrator vehicles.  The requirement was for a vehicle that could reach 16700 meters (55,000 feet MSL) and remain aloft for up to 24 hours.  The two Boeing/General Electric RPV demonstrator vehicles were identified as Boeing YQM-94 B-Gulls, Later re-identified to GQM-94 B-Gull. 

Two competitors, Boeing with the YQM-94 Compass Cope B and Ryan Aeronautical with the YQM-98A Compass Cope R (later the YGQM-98A) would eventually participate in the program.  The added “G” designation indicated a vehicle capable of takeoff and landing from improved runways (Ground).  The two competitors were similar in appearance, looking like long winged jet powered gliders with twin vertical stabilizers, retractible tricycle landing gear, and one engine pod mounted above the wing root.

Ryan Aeronautical YQM-98A R-Tern Compass Cope RPV

Ryan Aeronautical of San Diego CA proposed a competing RPV based on the Ryan Aeronautical Model 275 to the same specification and based on their long experience in building unmanned drones.  In June 1972 Ryan received Contract F33657-72-C-0840 to produce two prototype drones with the USAF identification YQM-98A R-Tern.  The Boeing entry was a “remote piloted vehicle” with a TV camera in the nose that had to be piloted by an operator on the ground.  Ryan took the approach of designing their entry as a true UAV “Unmanned Aerial Vehicle” that could fly a complete pre-programed mission using an onboard mini-digital computer or be controlled by a ground operator.

The Ryan Model 275 pictured below was capable of meeting the specifications of the Compass Cope program with the possible exception of 24 hours endurance.

Over the next 18 months Ryan Aeronautical would complete a total redesign and re-engining of the vehicle resulting in an entirely new RPV (UAV), and construct two prototype YQM-98A R-Tern vehicles.  The new Ryan Aeronautical entry would be capable of autonomous flight (fully automated hands off) for an entire 24-plus hour mission.  The new vehicle would have a top mounted Garrett (Airesearch Manufacturing Company CA) designed ATF3 development engine and two vertical stabilizers.  The selected Garrett ATF3 engine has a very low TSFC (Thrust Specific Fuel Consumption) of 0.44 Lb/Hr/LbFn (pounds per hour per pound of thrust) and low smoke and IR (Infra Red) emissions.  The two photos below show the RPV Takeoff and the RPV on the ground at Pima Air Museum in Tucson AZ.  The second photo is a good indicator of the Ryan YQM-98A wing span.  The YQM98A is no longer at Pima Air Museum.  It has been sent to another Museum.

During the Ryan YQM-98A redesign the Garrett Corporation was building two ATF3 development engines SN #16 & #17 for high altitude testing at NASA Lewis Research Center to confirm acceptable high altitude performance for the Ryan Aeronautical YQM-98A R-Tern RPV.  Site B Performance Engineer John Huber said that ATF3 Engine #17 exceeded all Compass Cope performance requirements as well as the demonstrated performance of all other engines tested at NASA Lewis Research Labs for this contract.  At the end of testing everyone agreed that they should go for broke to determine maximum ATF3 engine capabilities.  Engine #17 demonstrated a “Locked Throttle Climb” from 15,000 to 55,000 feet MSL (with the EEC automatically adjusting engine N1 to hold a constant ITT during climb and/or cruise with no throttle adjustments), a first for any Turbofan Engine.  The Electronic Engine Control (EEC) Locked Throttle climb/cruise feature eliminates the danger of undetected engine over-temperatures while greatly reducing operator workload.  Altitude test conditions at NASA Lewis were increased up to 100,000 feet MSL and Mach = 0.8.  ATF3 engine #17 continued to make usable thrust at 100,000 feet MSL (15 LbFn net) with all engine parameters within acceptable operating limits and NO Tt8 (ITT)  (Interstage Turbine Temperature) limit exceedances.  Turbine temperature was the same as at 40,000 feet MSL.  Comments from cell operators; “This is the first time we has positive Thrust bu any Turbofan Engine at these Conditions.”

John Huber informs me that the Garrett personnel involved in the above test were Test Engineer Gerry Steele, Performance Engineer John T. Huber, and Controls Engineer Jack White.  John said we were all sitting on pins and needles until the test was completed and the Test Cell Director said “That is the best we can do.  End of Test.”  The Test Cell Director said that this was the first time he saw a positive thrust on a Turbofan engine operating under these conditions.

As you can see from the Garrett YF104-GA-100 Turbofan engine photo below this engine was a pre-productions pre-certification development engine that was substantially different from current production ATF3-6 and ATF3-6A engines that were completely redesigned in 1975, and they are NOT interchangeable.  No ATF3-6 or ATF3-6A FAA certified Turbofan Engine will physically fit either of the two Ryan YQM-98A airframes.  The main mount on this engine is on the crossover-duct fully 3-1/2 inches forward on the current main mount location on the midframe assembly (and away from turbine disk planes).  The forward mount on the Cast Aluminum Front  Frame will not mate up with Ryan YQM-98A engine mount.  The only three engines capable of mounting to the Ryan YQM-98A airframes were ATF3 Prototypes SN’s P-1, P-2, & P-3 that were destroyed during a Garrett Site B Torrance CA cleanup in the late 1980’s.  Several employees including Site B Test Supervisor Clyde Hill Jr. and myself were unable to garner any interest in preserving these unique engines for museums.  They are now lost to history forever.  This site contains three photos of ATF3 engines SN 16 &17 in test cell ducting at NASA Lewis Research Center on the “Photos page.”  These photos are thumbnails to larger photos.

The two completed Ryan YQM-98A RPV’s had their nose and tail sections removed and were loaded into a Lockheed C5A aircraft at Ryan Aeronautical in San Diego CA for transport to Edwards AFB CA in April 1974 for final assembly, calibration, checkout, and testing.  After arrival at Edwards AFB the two Ryan YQM-98A RPV’s would undergo 3-months of intensive training and flight simulations.

Ryan Aeronautical YQM-98A System Redundancies

The Ryan YQM-98A vehicles have dual Electrical System redundancy

-    Direct Current Generators with dual Battery Backup

-    Alternating Current Inverters with Alternating Current Generator Backup


The Ryan YQM-98A vehicles have total dual redundancy in Vehicle Control System Actuators, Gyros, Sensors, Engine Power Levers, and all Electronic Components, and in addition the Landing Gear and Brakes have Pneumatic Backups. 

Ryan Aeronautical YQM-98A Flight Control Redundancies

Unlike the Boeing YQM-94 B-Gull with only ground operator control, the Ryan YQM-98A R-Tern vehicles have an onboard mini-digital computer capable of flying an entire pre-programed mission from initial climb through brake application after touchdown.  The YQM-98A onboard mini-computer has total redundant system switching capabilities, and operation of the vehicle can be taken over by ground personnel if necessary.


In Command Link control system redundancy becomes quadrupled

  1. -   Two separate MCGS (Microwave Command Guidance System)

  2. -   Dual UHF (Ultra High Frequency) Guidance Systems

Any of these four links can fly an entire mission.  If necessary a ground operator can take control of the vehicle.

TALAR (Tactical And Landing Approach Radar)

The Ryan YQM-98A has a fully automated approach and landing system (TALAR) as well as two backup landing systems, the semi-automatic and manual landing systems.  The TALAR system is capable of autonomous control of the vehicle landing from 4,000 feet AGL through touchdown and initial rollout to 75 Knots when brakes are manually applied.  TALAR system equipment consists of;

  1. -   One TALAR Microwave Transmitter at the approach end of the runway that emits four microwave beams, two  glide slope beams and two azimuth beams.

  2. -   One TALAR Microwave Transmitter at the departure end of the runway that emits one microwave azimuth beam down the runway centerline.

  3. -   One vehicle onboard TALAR Receiver to receive TALAR Transmitter signals.

  4. -   One Radar Altimeter input to the onboard Mini-Computer.

  5. -   One vehicle onboard Mini-Computer to receive and discriminate the TALAR and Radar Altimeter signals and command control functions for necessary flight path corrections.

TALAR system calibration and checkout using Beachcraft King Air 90

A specially modified Beachcraft 90 aircraft with TALAR Receiver and Radar Altimeter was used to functional test the Ryan YQM-98A automated landing system without risking either of the two test vehicles.  The vehicle onboard Mini-Computer automatically activates TALAR for approach and landing when the Radar Altimeter indicates that the RPV has descended to 4,000 feet AGL (Above Ground Level).

LONGEST FLIGHT, Ryan Aeronautical YQM-98A R-Tern

On the morning of Aug 17, 1974 at 0530 hours, the Ryan YQM-98A onboard mini-computer performs a complete vehicle system checkout in just 20 minutes that would normally have taken 24 hours if accomplished manually.

The Garrett ATF3 engine was started, umbilicals removed, and the primary ground controller taxied the vehicle into position on the runway centerline.

Brakes released and throttles advanced the Ryan YQM-98A accelerates toward the TALAR Transmitter at the departure end of the runway braking ground and initiating climb in about half a minute.

The Ryan YQM-98A continues to climb at takeoff power for three minutes (from brake release), then is switched to automatic control by one of the MCGS onboard control systems.  The RPV will continue to climb at Mach=0.55 to the assigned altitude 55,000 feet MSL.  Any additional climb will be due to fuel burnoff.  The entire flight will be automatically controlled by the Ryan YQM-98A’s onboard mini-computer.

After approximately 27-1/2 hours of fuel burnoff the Ryan YQM-98A with the Garrett ATF3 engine at idle and the RPV spoilers fully extended is climbing toward “Coffin Corner” (an altitude where the aircraft stall speed and never exceed speed {Vne} are identical).  The fear was that if allowed to continue the only way to get the RPV down would be an engine shutdown and dead-stick landing.  The decision was made to extend the landing gear increasing drag and initiating a decent.  Once the RPV altitude had decreased sufficiently the landing gear was retracted.  With the exception of the landing gear extension and retraction the RPV remained under MCGS fully automatic control.

Once the RPV had descended to 4,000 feet AGL (Above Ground Level) the Radar Altimeter triggered the onboard Mini-Computer to hold 4,000 feet AGL and switch to TALAR for approach and landing.

At a predetermined point the Ryan YQM-98A initiated at 4-degree glide path (13.5 Ft - Sec) rate of decent (810 Ft - Min) to TALAR intercept.  After TALAR intercept the vehicle glide slope and runway alignment is controlled by TALAR.

TALAR will maintain wings level throughout approach and landing to avoid wingtip contact with the ground.  Any course corrections to maintain runway alignment will be accomplished through slew commands to the rudders. 

AT 70-feet AGL the onboard mini-computer will initiate ”auto flare” with a 2-degree nose up pitch command to the elevators, and a decent rate of 2 feet - second to touchdown.   TALAR approach transmitter is deactivated at flare.  The TALAR departure transmitter will maintain runway centerline alignment.

At 15 feet AGL the onboard mini-computer will take out any crosswind induced vehicle yaw with a “de-crab” command to the rudders while maintaining wings level to touchdown.  At touchdown the mini-computer will command elevators fully down and extend spoilers to reduce lift and maintain nose wheel contact with the ground for directional control during rollout.

At approximately 75 Knots the brakes are manually applied and the primary ground controller takes control of the vehicle for taxi and shutdown.

During the Ryan Aeronautical YQM-98A’s record setting flight on 17/18-Aug-1974 the Ryan/Garrett RPV established altitude and endurance records for vehicles in the 5,000 pound thrust class.  The flight lasted 28 hours 11 minutes 12 seconds and landed with 6 hours of fuel remaining in the tanks.  The Ryan YQM-98A met or exceed every USAF Compass Cope program requirement, and exceed the Boeing/GE YQM-94 B-Gull  demonstrated survivability and performance as well. 

During four months of testing the Teledyne-Ryan YQM-98A met or exceeded every USAF Compass Cope program requirement.

  1. -   Both Ryan airframes survived with no damage.

  2. -   The Garrett YF104-GA-100 engine never failed to start even with temperatures exceeding 125 degrees F, when T-38 trainers were grounded with temperature limited hung starts.

  3. -   The Teledyne-Ryan YQM-98A met or exceed all USAF Compass Cope program and flight objectives.

  4. -   The only place where the Teledyne-Ryan YQM-98A failed to beat out the Boeing YQM-94A competitor was cost, when the vehicle capabilities and survivability were not considered.

ADDITIONAL BENEFITS of the Ryan Aeronautical YQM-98A R-Tern Design

The Teledyne-Ryan YQM-98A Compass Cope RPV’s extensive use of composites and the selection of the Garrett ATF3 Turbofan engine resulted in a very Stealthy Aircraft, indeed.   The use of composite structures, a trapezoidal fuselage cross-section, and the low TSFC, smoke and IR emissions of the Garrett ATF3 engine (YF104-GA-100) mounted above the fuselage resulted in a high altitude long endurance RPV, virtually undetectable either visually or by Radar and Infrared sensors. I have been told that if the U-2 chase aircraft pilot lost visual contact with the Ryan R-tern the pilot could fly circles around it and still be unable to locate the RPV visually by smoke emissions or by using his onboard IR Sensors and Radar.  Ground control would have to vector the U-2 away from the area, and then vector the U-2 back toward the Ryan YQM-98A at the same altitude until the pilot visually reacquired the Ryan R-TernThe long and short of it is, if you can NOT locate the RPV/UAV you will not know it is above you watching, and will not be able to acquire it or shoot it down.

The USAF Compass Cope Contract was awarded to Boeing/GE based on cost alone, with no consideration given to vehicle survivability and performance or competition results.  Boeing/GE proposed a redesigned vehicle to meet the Ryan Aeronautical YQM-98A’s demonstrated performance.   Ryan Aeronautical challenged the contract award based on competition results, “WE WON!”  It became a moot point when the USAF Compass Cope program was canceled in July 1977. 

The USAF Compass Cope Program may have been cancelled , however, you have to believe that the results of the Teledyne-Ryan YQM-98A R-Tern RPV/UAV testing proved the viability of the concept ultimately resulting in todays Northrup-Grumman Global Hawk UAV’s.  

You can view one of these unique Ryan Aeronautical YQM-98A RPV/UAV airframes at the Pima Air Museum just east of Tucson AZ on the North side of highway 10.

If you have additional information about the Ryan Compass Cope YQM-98A or would like to contact the ATF3 Online Museum curator please email me.


Last updated  5/24/2011