Operating Limitations


     The minimum crew required for the accomplishment of a drone mission from launching to landing is the deck controller and the CIC controller. This assumes that the drone has been spotted at the launch area and secured to the deck with a tie down device which has a remotely actuated disconnect.


    All the instruments used in the operation of the drone are mounted on the panel of the control monitor. With the exception of the elapsed time indicator, these instruments function only while the umbilical cables are connected to the drone and the system is energized. The instruments serve to monitor drone readiness for launching. Certain of the instruments provide a go no-go indication; the remainder provides a quantitative indication. The instrument markings are shown in figure 1 of this section and are explained, where necessary, in the following paragraphs.


NOTE: The follow-up position meters are not shown in figure 1 since their indications are proportional to the magnitude of the command inputs. Refer to the section “Normal Procedures”.




    Engine exhaust gas temperature will vary with ambient temperature. Refer to the "Performance Data" section for charts of exhaust gas temperature versus ambient temperature.



    The transmission oil temperature indicator light goes on if the transmission oil temperature becomes excessive. If the light goes on, stop the engine immediately, observing the proper procedures described in the section “Normal Procedures”.


    The transmission oil pressure indicator light goes on if transmission oil pressure is inadequate and when the transmission is static. When the engine is started, the light should go out within 35 seconds after the cranking cycle is started. If the light goes on during operation, stop the engine immediately, observing the proper procedures described in the section “Normal Procedures”.


    The voltage monitor should indicate within the acceptable area at each of the switch positions I through 9, except that on position 1, the indication may be to the left of center. Position 10 is not used.



    The altitude synchronization meter should indicate within the green band before power is transferred to the airborne generator (control monitor TRANSFER switch from AUX to DRONE).



    The gyro slaving meter should indicate within the green band or oscillate uniformly and equally beyond each side of the green band (not hitting the stops) before power is transferred to the airborne generator.


Figure 1: Instrument Markings



    Engine output speed and power are controlled within limits by the fuel control unit and the power turbine limiter. The power output required of the engine is determined by the aerodynamic loading of the rotors.

Engine Fuel is grade JP-5, Specification MIL-T-5624.

Engine operating limits are shown in figure 2. The engine must be sent to an overhaul facility if any of the following time, temperature, or speed conditions occur:

1.    Average Exhaust Gas Temperature (EGT) exceeds maximum starting or transient temperature limit, as applicable.

2.    Average stabilized EGT exceeds maximum stabilized temperature limit more than five times.

3.    Average EGT has exceeded the maximum stabilized temperature limit by 30º F for more than five minutes.

4.    Gas producer speed exceeds 40,200 rpm or output shaft speed exceeds 7200 rpm (120%)




Shaft horsepower
    Interstage bleed valve active

    Interstage bleed valve inactive

Military rated

Nominal available

330 at 90º F
365 at 59º F

300 at 90º F
330 at 59º F

Gas producer speed

Maximum allowable

40,200 rpm*

Output shaft speed


6000 rpm (610 rotor rpm)

Engine Oil Pressure

Flight idle to rated power

30 psig, minimum
70 psig, maximum

Engine Oil temperature

Flight idle to rated power

250º F, maximum, out of cooler

Engine exhaust gas temperature

Transient Starting

1200º F, maximum
1270º F, maximum

Maximum allowable stabilized EGT
   Interstage bleed valve active
   Interstage bleed valve inactive

At Rated Power

Refer to "Performance Data" Section
Refer to "Performance Data" Section

* This parameter can be monitored only when the Engine-Rotor System Test set AN/USM-202 is connected to the drone. Refer to the "Power Plant, Fuel and Related Systems" handbook; NAVAIR 01-150DHC-2-4.



Within the flight envelope, rotor speed is automatically maintained within fixed limits by the engine control system and, in the event of rotor overloading, by an electronic rpm cross-feed limiting system.

The rotors are driven by constant mesh gearing by the engine power output section; no clutch is provided. When the engine is started, the rotors are brought to flight idle rpm within approximately 60 seconds.

      If rotor speed exceeds 762 rpm (125 %) the rotor assemblies must be sent to an overhaul facility for inspection for possible overstress.


Airspeed limitations are set forth under the paragraph headed MAXIMUM VELOCITIES in this section.

Except as otherwise required during launching and landing, a forward true airspeed of 30 to 60 knots should be maintained during ascents, and 40 to 60 knots during descents.



Acrobatic flight with the QH-50D drone is prohibited.

    For purposes of acceleration during launching and landing, the maneuver stick (in the maneuver mode only) can provide command authority in excess of that normally required for these purposes. Excessive deflection of the maneuver stick can cause the drone to exceed its flight envelope airspeed limitations. Sudden large reversals of stick deflection should be avoided. The danger inherent in such practice increases when the drone is in the heavy weight configuration. As the drone begins to respond to a large maneuver stick command input, the command must be reduced smoothly until a steady state safe flight attitude is attained. For all normal flight operations in the maneuver mode, a maximum of approximately 30 percent of maneuver stick displacement from neutral should be adequate. 

If, in emergency, it is necessary to exceed 30 percent of stick displacement, the requirement for smooth, gradual movement of the stick becomes more critical.

    In both the maneuver and cruise modes, it is possible to apply simultaneous collective and cyclic pitch command inputs of sufficient total magnitude to cause the power required to exceed the power available. If this demand is maintained, engine and rotor rpm will drop, and collective limiting will occur. It is not possible to determine an absolute magnitude of command input at which this will occur, due to the contributory effects of ambient temperature, barometric pressure, and drone gross weight. Airspeed and altitude commands must be coordinated smoothly to prevent excessive collective limiting. High g-load maneuvers such, as rapid changes in airspeed commands and sudden large changes in altitude command should be avoided, except as required during launching and landing operations. Normal operation in the maneuver mode should be limited to 300 yards, maximum.



    Hovering at zero airspeed requires more power and consumes fuel at a greater rate than does directional flight at low and moderate speeds. Under conditions of high ambient temperature and/or low barometric pressure, in combination with drone heavy weight configuration, prolonged hovering should be avoided.

    If the drone is being hovered over the flight deck against a relative wind, it has the advantage of the lift (or airspeed) proportional to the velocity of the relative wind. In moving the drone away from the destroyer, this airspeed must be maintained until the drone is clear of the destroyer, and then gradually increased to move the drone upwind. In this manner, lift increases as the drone moves out and a safe flight regime is maintained.

    If the opposite procedure is followed; i.e., if the airspeed required to hover over the deck is reduced and the drone is allowed to drift down wind, the drone will reach a point of zero airspeed, with respect to the surrounding air mass. As this occurs, the power required increases, and, under marginal conditions, settling will occur.



    The turn rate of the drone is inversely proportional to forward airspeed. When a large heading change is commanded rapidly, the drone executes the turn; but, because its turn rate is limited, it lags behind the heading pointer. Under certain circumstances, a sudden reversal of the direction of turn will occur. The heading card is provided with two diametrically opposed white sectors; one in the 0- to 90-degree quadrant, and one in the 180- to 270-degree quadrant. In commanding turns greater than 90 degrees in which either a full white or a full black sector will be spanned, the drone heading must occupy the sector being spanned before the heading pointer is turned out of that sector. For example: if a turn from 80 degrees to 190 degrees is to be commanded, the drone heading must actually have passed 90 degrees before the heading pointer is turned past 180 degrees on the dial. Failure to follow this procedure will result in an inadvertent turn reversal and may result in the loss of the drone.

 Figure 3, left, shows the calculated times required to complete turns as a function of airspeed and turn increment. This plot is based upon the turn rates programmed into the drone. With a fixed bank angle in coordinated turns in the cruise mode, the turn rate is automatically programmed to satisfy the turn coordination requirements. The same turn rates apply when in the maneuver mode, even through the bank angle is not present. Failure to observe the time limitations shown in figure 3, prior to commanding a turn in the opposite direction, will result in a turn reversal and may result in the loss of the drone. Deliberate heading command reversals should be avoided.

    The phase of the roll signal in coordinated turns is related to the direction of the change in drone heading; not to the forward or rearward movement of the drone through the surrounding air mass. If, in rearward flight in the cruise mode, a turn is commanded, the rotors will tilt in the direction appropriate to the change in fuselage heading. In rearward flight the rotors will tilt toward the outside of the turn, instead of toward the center and a mis- coordinated turn will result. For this reason, while the drone is in rearward flight in the cruise mode, turn commands must not be made.


     The altitude command capability of the shipboard guidance system is from -200 feet to +1000 feet. This range normally is directly related to the elevation of the operating site; not to sea level. Thus, if the elevation of a shore based operating site or fleet introduction site is 1000 feet above sea level, the operating range of the drone, with respect to sea level, is 800 to 2000 feet. This characteristic is due to the fact that the barometric altitude control synchronizes (establishes its zero reference altitude), prior to launch, at the ambient barometric pressure at the launching site.

    In making a shore to ship transfer in which the sending station (shore based site) is more than 100 feet, but not more than 900 feet above sea level, the barometric altitude control must be synchronized (zeroed) at an artificially induced static pressure prior to launch. This operation requires the use of the Altitude Controller Test Set VPT- 10G (seen above left). The procedure is described in the section, “Normal Procedures” under the paragraph headed TRANSFER, ALTITUDE TO SEA LEVEL.

    Transfer from an elevation greater than 900 feet to sea level cannot be accomplished with the QH-50D system. Transfers from elevations greater than 750 feet must be accomplished without weapons.




    The center of gravity and weight of the drone are fixed within a well-defined envelope because of the limited number of variables, which are:

1. Fuel quantity remaining.

2. Number and type of weapons carried.

    The average fore and aft CG location has been determined to provide an adequate margin of longitudinal cyclic pitch control in all weapon configurations. It is essential that recommended weapon-loading procedures be adhered to and that no unauthorized equipment be installed on the drone.

    General information on Mark 44 and Mark 46 torpedoes and their accessories is contained in U. S. Navy Aircraft Torpedoes, Accessories and Trajectory Data (NAVAIR OP 1207, Fourth Revision with Change 1). The information contained in that publication relating to the fore and aft positioning of the suspension bands is not applicable to the QH- 50D drone. The center gravity of the Mark 44 torpedo with Mark 24 air stabilizer attached, and Mark 46 torpedo with Mark 31 air stabilizer attached, must be located 2. 7 ±0. 25 inches forward of the mast centerline. (Refer to NAVAIR 01-15ODHC-2-1, General Information and Servicing, for weapon installation data specific to the QH-50D drone).


    Airspeed calibration data (true airspeed versus command readout) for the various Mark 44 weapon configurations is included in the “Performance Data” section.  Airspeed calibration data for the drone with Mark 46 weapon store will be supplied when available.

    Automatic compensation is provided for lateral center of gravity shift as one of two side-by-side weapons is dropped. The compensation is inherent in the design of the system; no weapon sensing devices are required. (Refer to “Flight Characteristics” section)

    The fuel tank is close enough to the average center of gravity of the drone that the expenditure of fuel has no significant effect on the flight characteristics of the drone.

    The drone is equipped with mounting provisions for an operational telemetry package consisting of the following components:

Telemetric Data Transmitter T- 1014/AKT- 20

Multiplexer TD- (TBA)/AKT-20

Fuel Level Sensor DT-324/AKT-20

Five ballast weights, fastened to the forward side of the avionic panel, must be removed when the operational telemetry components are installed.




The operating flight envelope is defined below (Refer also to the “Performance Data” section).


      The limitations set forth in the following paragraphs constitute the flight envelope of the QH-50 drone in its configuration as of June 15, 1967. Any changes to, or expansion of, the flight envelope will be set forth in subsequent revisions of this section.



The true airspeeds listed below shall not be exceeded. Refer to the airspeeds calibration data in the "Performance Data" section for the command readout required to produce the desired true forward airspeed of the drone.

Direction and Configuration

True Airspeed
in Knots

Forward, all configurations


Lateral: Maneuver mode, all configurations


Rearward: Maneuver mode, all configurations



AVOID High G-Load Maneuvers in all configurations and at all airspeeds.




Within visual range of controller (actual)....

0 to 1000 feet

Beyond visual range of controller (commanded)...............

300 to 1000 feet

Rate of change of command..............

300 feet per minute
(5 feet per second)
using the ALTITUDE knob; otherwise limited by the ALTITUDE RATE switch


AVOID abrupt altitude commands during steady state flight conditions. 
Do not exceed the 300-foot per minute rate of change of command, ascending or descending.


    Refer to the weapon drop envelopes in the "Performance Data" section.

The weapon drop envelopes shown in the “Performance Data” section are based solely upon the requirements of the Mark 44 torpedo with Mark 24 Mod 2 air stabilizer and Mark 46 torpedo with Mark 31 Mod 0 air stabilizer. The entire envelopes shown in the charts may be used when the drone is within visual range of the controller. When the drone is beyond visual range of the controller, a minimum commanded altitude of 300 feet must be maintained, due to the air speed versus altitude characteristics of the drone described in the “Flight Characteristics” section



Drone altitude
in feet

Range in
nautical miles












The drone has the capability of accomplishing the mission described below, based on normal gross weight at launch and 80 knots Vmax, to a maximum combat radius of 40 nautical miles.

1.   Warm up and launch in 1/2 minute

2.   Cruise out at Vmax air speed

3.   Loiter out of ground effect for 38 minutes

4.   Cruise back at Vmax, retaining weapons

5.    Land

Note: Refer to "Performance Data" for fuel consumption and endurance data.



The maximum allowable single continuous turn in the cruise mode is as follows:

At ambient temperatures of 65º F or
less, 0 to 80 knots, true airspeed..................180 degrees

At ambient temperatures greater than 65º F,

    0 to 20 knots, true airspeed............45 degrees
    20 to 80 knots, true airspeed.........180 degrees

    In order to prevent turn reversal, turns exceeding 80 degrees must be accomplished in successive command increments not exceeding 80 degrees for each increment. The times required to wait between turn commands at various airspeeds is a function of the turn rates programmed into the drone. The calculated times required to complete turns, as a function of airspeed and turn increment are shown in figure 3.

    Any single commanded incremental airspeed change of more than 30 knots requires a minimum delay of 5 seconds before commanding a turn.


    Launches and landings should not be executed when deck motion exceeds a total roll travel of 7 degrees and a total pitch travel of 2 degrees.


    During the time the roll and pitch gyro is running down (approximately 20 minutes), the drone should not be subjected to steady state motion about the yaw axis at a rate greater than 60 degrees per second, or momentary motion about the yaw axis at a rate greater than 200 degrees per second for more than 0.1 second.


    Drone operations may be curtailed under adverse weather conditions at the discretion of the operating activity.


End of Operating Limitations Section


Home Up Description Normal Procedures Emergency Procedures Auxiliary Equipment Operating Limitations Flight Characteristics Systems Operation Crew Duties All Weather Ops Performance Data


Helicopter Historical Foundation
P.O. Box 3838, Reno, Nevada USA 89505

Because of SPAM, we ask that you copy the below address into your mail program and send us your comments!

Email us at: Gyrodyne_History@Yahoo.com

The name "Gyrodyne" in its stylized form above, is the Trademark of and owned by the Gyrodyne Helicopter Historical Foundation; unauthorized use is PROHIBITED by Federal Law.

All Photographs, technical specifications, and content are herein copyrighted and owned exclusively by Gyrodyne Helicopter Historical Foundation, unless otherwise stated.  All Rights Reserved ©2013.

The Gyrodyne Helicopter Historical Foundation (GHHF) is a private foundation incorporated in the State of Nevada as a Non-profit organization. 

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.
Your support will allow for that work to continue.