The Model QH-50E

    When Boeing ceased building its 365 shp model 550-1 turbo-shaft engine (military designation T50-BO-12) in April 1968, Gyrodyne sought other engines to power its dynamic rotor system and provide the Navy the opportunity to not cancel the UAV program due to Boeing's exit. 

   What began as the Allison powered YQH-50E test vehicle, as seen left, became the QH-50E. The initial Allison T63-A-5A, Model 250-C19A, free turbine type, gas turbine engine used in the YQH-50E, was rated at 317 SHP at sea level, standard conditions. 

    The QH-50E was designed and fabricated under Naval Air Systems Command Contract No. N00019-69-C-0361 which was authorized by the United States Navy on December 31, 1968. 
    Although only three aircraft were delivered to NATC, Patuxent River, Md. for stability and control tests in 1969 under that contract, 3 subsequent QH-50D aircraft were later converted into E's by the installation of the Allison power package. The QH-50E is currently the final variant of the QH-50 series helicopter.

As the QH-50E was produced in a limited amount, its U.S. Naval service history is limited to the testing of the engine combination only. Upon the engine qualification that the Navy accepted, all further QH-50 orders were cancelled in 1969 due to Navy down-sizing and the scrapping of many of the ships the QH-50 operated from.
  As the Allison powered QH-50E was seen then, as it is today, as the progenitor to expand the mission capabilities so adequately illustrated by the D model, we herein submit a detailed description of the E model to illustrate what an Allison powered QH-50 would look like. 

The Difference

    The only difference between the D and E model QH-50, consist of installing a new engine and engine attachment (see photo-above left), and altering the direction of flight, which is the reverse of the Model QH-50D in that the engine is installed aft of the rotor mast and the avionics equipment, flotation equipment and fuel tank are forward of the mast.

    Like the D model, the QH-50E rotor system is of the two-bladed coaxial semi-rigid type, incorporating fiberglass blades of a 2:1 taper ratio with a negative twist of 12 degrees. The Model QH-50E was designed like the D, to be capable of carrying and launching two (2) MK44 Torpedoes, or one MK46 Torpedo, or a special weapon payload of 1500 lbs.

The Fuselage 

    The lower casting of the transmission forms the main portion of the fuselage. Attached to the casting are the four supporting struts for the skid-type landing gear, the bomb shackle mechanisms, and two upper and two lower support tubes. The fuel tank is mounted on the lower two tubes of the forward truss assembly and is positioned directly ahead of the transmission casting. The tank is further secured by a forward panel and the upper two tubes of the forward truss assembly. This panel also serves as a mounting board for some components of the Automatic Stabilization and Remote Control Equipment (ASCE), as well as other equipment such as flotation gear and operational telemetry; see figure at right.


The Transmission

    The rotor transmission system consists of a two-stage gear reduction system, two rotor drive shafts, an integral lubricating system, a generator drive, and a four-axis servo actuator drive. Power from the engine is transmitted to the rotors through the two-stage gear reduction; the second stage of which divides the torque to the two contra- rotating coaxial rotor drive shafts. The generator drive and four-axis servo actuator drive are connected by gears to the outer (lower) rotor drive shaft.


The Rotor System

    Two 2-bladed semi-rigid contra-rotating coaxial rotors comprise the rotor system. The blades are of glass fiber reinforced plastic construction - incorporating linear taper in planform and thickness and 12 degrees negative twist. The Model QH-50E vehicle is completely controllable through the rotors. Rotor controls are operated by the Automatic Stabilization and Remote Control Equipment (ASCE). Control in pitch and roll is achieved through conventional cyclic control of the swash plates. Collective pitch control is obtained by conventional collective movement of the swash plates. Control in yaw is achieved by means of rotor blade tip-mounted air (drag) brakes. Movable tip brakes are located at the tips of both the upper and lower rotor blades and provide, by their deflection, positive directional control in all conditions of flight by creating an unequal torque distribution in the rotor system. A left turning moment results from lower rotor tip brake deflection while a right turning moment results from upper rotor tip brake deflection. In the neutral condition, both sets of tip brakes are undeflected.


Power Plant

    The power plant for the Model QH-50E vehicle is the T63-A-5A, Model 250-C19A, Allison gas turbine engine. The gas producer section is composed of a combination six-stage axial flow one-stage centrifugal flow compressor directly coupled to a two-stage gas producer turbine. The power turbine section is composed of a two-stage free turbine which is gas coupled to the gas producer turbine.  The engine incorporates an integral reduction gear box which provides an internal spline output drive at the front of the gear box. The power plant has a take-off power rating of 317 SHP at 6,000 rpm, at sea level standard conditions. The engine is attached rigidly, by means of a cast aluminum mount, to what is now the rear face of the transmission. This face was fwd and where the Boeing engine was mounted in the QH-50D. The engine intake is behind and below the transmission and faces forward and the engine exhaust is directed outward and downward. A transmission input power drive shaft connects the engine with the transmission first stage gear system and runs inside the engine mount.

    Today, there is only one QH-50E that survives of the three originally converted from D models; that being DS-1717 (see below for the fate of DS-1718 and DS-1719). DS-1717 resides in a storage building at White Sands Missile Range, New Mexico, parked among some 20 surviving QH-50D model aircraft requiring overhaul before flight.

     While DS-1717 sits among it brethren D models, its future is uncertain as its' uniqueness as a prototype invalidates its further use other than for parts for the D models currently flown for Army missions. The Gyrodyne Helicopter Historical Foundation is dedicated to the saving of this "one of a kind" aircraft so that future generations can see the combining of the QH-50 Co-Axial rotor system to the currently available Allison (now Rolls Royce) 250 series engine. Its use as an educational tool illustrating that engine-coaxial rotor combination, is incalculable. 

    Despite the QH-50E being a prototype aircraft, the increase in payload due to the lower weight Allison engine provides such increased benefits, that the information below is herein provided so that the performance criteria using the lower horse powered C-19 can be seen; Imagine if this aircraft had the use of the Allison 250-C20B (420 Shp).......


Take-Off Loading Conditions- ASW Attack, 2 qty, MK-44 Torpedoes, Full Reg. Fuel (no aux fuel)

First Flight of QH-50E was on September 11, 1969



The Model QH-50E Drone is a remotely controlled rotary-wing ASW weapon carrier designed to deliver alternate weapon loads of 920 lb or 1140 lb. Combat radius of the-drone is about 40 nautical miles with 4 hour loiter, depending on loading condition, at a cruising speed of 80 knots. The drone incorporates two two-bladed counter-rotating coaxial rotors of the semi-rigid (see-saw) type.
    The blades are of fiberglass construction, incorporating linear taper in planform and thickness and negative twist. The machine is completely controllable through the rotors. Rotor controls are operated by the automatic stabilization and remote control equipment (ACSE).
    Control in pitch and roll is obtained through conventional cyclic control of the swash plates. Control in yaw is achieved by movable tip brakes connected to both the upper and lower rotor blade tips and provide positive directional control by creating unequal torque distribution in the rotor system. 
    The power plant is the 317 shp T63-A-5A Allison Free-Turbine engine permitting connecting the engine drive directly to the transmission without a clutch installation.

Engine (1) T63-A-5A  Empty   993.0 Lbs
Manufacturer Allison Engine (Rolls Royce) Normal Gross I 2184.3 Lbs
Type Turboshaft Normal Gross II 2288.3 Lbs
Engine is six axial flow with single centrifugal flow compressor coupled directly to two-stage gas producer turbine Normal Gross III 
(using 250-C20R)
3000 lbs 
  (1659 lb pay load)



  SHP RPM ALT No. of Tanks Gallon Cap. Location
Military 317 6000 SSL One 52.0 gals Fwd of Trans.
Normal 270 6000 SSL Grade of Fuel: JP-4 (Mil-J-5624F92)


AN/ARW-78 (1 each) Radio Rec. Set Capacity: 3.1 gallons
AN/ASW-20 (1 each) Automatic Flight Control Set Specification: MIL-L-23699
  Fuel & Oil weight  348 LBS.
  Empty weight

 993 LBS.


 947 LBS.

  Disc Loading
    (lb/sq. ft.)


  Max. Speed/altitude

80 knots/S.L.

Cruise Speed 
at Sea Level to target (no shroud)
70 knots
Combat Range 155 miles
Hover: (OGE) 6250 ft.
Hover: (IGE) 11,500 ft 
Vertical Rate of Climb at Sea Level 1900 fpm
Maximum rate of climb at Cruise 1255 fpm


Serial Number History

QH-50E Drone (also known as YQH-50E)

Serial Numbers

Number Produced

Manufacture Date


DS-1717 (seen above) 1 Originally accepted as a D model in April 1969

Returned and remanufactured as an E model in August 1969

Built under contract N00019-69-C-0361, DS-1717 originally was a QH-50D that was returned to Gyrodyne under a bailment agreement that included DS-1717,18 and 19. Delivered to NATC-Patuxent River, MD for stability and control tests, engine problems caused DS-1717 to be grounded while performing ground vibration tests. The program was cancelled before DS-1717 could be returned to service. It is presently stored in a U.S. Army Warehouse in New Mexico awaiting disposition.
DS-1718 1 Originally accepted as a D model in April 1969

Returned and remanufactured as an E model in August 1969

DS-1718, after completing preliminary control flights, was returned to Gyrodyne and converted into a two place, manned test bed for the 24' rotor system in which the Allison engine remained installed. Unfortunately, DS-1718 was destroyed in a trucking accident while being transported to California in November 16, 1999.
DS-1719 1 Originally accepted as a D model in April 1969

Returned and remanufactured as an E model in August 1969

DS-1719, upon acceptance by the Navy, was the more used E model during contractor demonstrations at NATC-Patuxent River, MD. It was used to attain information on the Allison engine installation and validity of its design. Unfortunately, a "hunting" problem would occur when the aircraft was close to the ground as the engine's fuel controller attempted to match the power required to maintain the set altitude the automatic flight control system was trying to maintain through increasing pitch of the rotor hubs. A time lag between when the power was needed and when it was delivered caused the engine systems to search for a balance of power. Gyrodyne attempted to fix the problem but this problem led to the loss of DS-1719 when it crashed while landing in November 1969. At that point the Allison powered YQH-50E development contract was cancelled.




Helicopter Historical Foundation
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GHHF is dedicated to the advancement of the education and preservation of the history of the Ships, the Men and the Company that built, operated and flew the U.S. Navy's QH-50 Drone Anti-Submarine Helicopter (DASH) System and to the preservation of the history of the U.S. Army's past use of DASH.
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