Gyrodyne QH-50

From Wikipedia, the free encyclopedia

The QH-50, better known as the DASH for Drone Anti-Submarine Helicopter, was a small, drone helicopter built by Gyrodyne for use as a long-range anti-submarine weapon on ships that would otherwise be too small to operate a full-sized helicopter. It remained in production until 1969. Several are still used today for various land-based roles.

DASH was a major part of the US Navy's FRAM program of the late 1950s. FRAM was started because the USSR was building submarines faster than the US could build anti-submarine frigates. Instead of building frigates, the FRAM upgrade series allowed the U.S. to rapidly catch up by converting older ships that were otherwise less useful in modern naval combat. The Navy was able to inexpensively upgrade the sonar on World War II-era destroyers, but needed a stand-off weapon to attack out to the edge of the sonar's range. The old destroyers had little room for add-ons like a full flight deck. The original DASH concept was a light drone helicopter that could release a nuclear depth charge or torpedoes. The aircraft was considered expendable.

The manned Gyrodyne XRON-1 Rotorcycle program of the mid-1950s provided prototype work for the DASH, and ultimately the Rotorcycle was modified to produce the initial drone version, the DSN-1/QH-50A The DSN-1 was powered by a Porsche YO-95-6 72 hp piston engine and carried one MK-46 homing torpedo. The next developmental version was the DSN-2/QH-50B that was powered by two Porsche YO-95-6 engines and also carried one MK-43 homing torpedo. Serial production of the DASH began with the third version, the DSN-3/QH-50C, in which a 255 hp Boeing T50-BO-4 turboshaft engine replaced the piston engines and the payload was increased to two MK-44 torpedoes. Three hundred and seventy eight QH-50C were produced before production ended in January 1966.

DASH's control scheme had two controllers, one on the flight deck, and another in the combat information center. The flight-deck controller would handle take-off and landing. The controller in the CIC would fly DASH to the target's location and release weapons using semiautomated controls and radar. The CIC controller could not see the aircraft or its attitude and occasionally lost operational control or situational awareness. Late in the program, there were successful experiments to add a television camera to the drone.

A tethered landing system was partially developed to land and take off in up to force-6 seas, but this was never deployed because submarines (the targets) could not launch missiles in hurricanes.

DASH came about because Gyrodyne had worked with the US Marines to develop a small, experimental co-axial helicopter for a scouting platform. A co-axial helicopter mounts two "main rotors" spinning in opposite directions to control torque, unlike the more common main rotor/tail rotor found on most helicopters. Co-axial rotors put more power into lift, and permit shorter rotor blades. Both traits help a helicopter to be as small as possible. On the downside, the blades must be kept very far from each other in order to avoid colliding, since the blades travel up and down as they rotate. This leads to increased complexity and decreased maneuverability.

For a drone, these tradeoffs were fine. For the DASH role, the original Marine version was modified with the addition of a turboshaft engine for improved performance, and the replacement of the seats and controls with a remote-control system and storage for two Mk.44 torpedos. In this form the DASH could be flown up to 22 miles from the ship, giving an incoming submarine no warning that it was actually under attack, at least until the torpedo hit the water.

Since it was expendable, DASH used off-the-shelf industrial electronics with no back-ups. the controls were multichannel analog FM. Over 80% of operational aircraft losses were traced to single-point failures of the electronics. 10% of losses were from pilot errors, and only 10% of losses were from engine or air-frame failures.

The DASH program was cancelled in 1969. Although low reliability was the official reason, the manufacturer pointed to the expenses of the Vietnam war, and the lack of any need for an antisubmarine capability in that war.

Modified DASH vehicles continued to operate for several more years in the Vietnam war. With attached television cameras, they were used as remote artillery spotters and organic reconnaissance by their ships.

A small number of DASH drones are still (2006) in operation at White sands test range, where they are used to tow targets and calibrate radars and electronic systems.