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de Havilland DH.117

Mach 2 High-Altitude Interceptor Proposal

United Kingdom | 1958

"A single mock-up was the only concrete evidence of the proposed de Havilland DH.117 interceptor intended for Britain before all was said and done."

Authored By: Staff Writer | Last Edited: 03/19/2019 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.
During the time of the Cold War (1947-1991) between East and West, British military power was to figure heavily into the defense of Western Europe should a Soviet invasion ever occur. This meant that its various service branches required all manner of modern technology to meet the threat of the day - namely that from nuclear-capable Soviet bombers.

Many aircraft designs were drawn up during the period to meet various demands: fleet air defense, day-night fighter, high-speed / high-altitude interceptor and so on. By the time of the mid-1950s, serious thought was being given by British authorities to shore up interception capabilities, particularly at high-altitude. This resulted in design studies and a formal requirement being penciled out by the latter part of the decades.

It was requested that a new, all-modern interceptor be developed that carried radar as well as strictly Air-to-Air Missile (AAM) armament controlled by an all-in-one weapon system. To go along with this, three critical factors came into play for Cold War-era interceptors: rate-of-climb, speed, and altitude. As such, a twin-engine (reheat-capable) design was all but necessary augmented by a limited-burn rocket booster unit. This would provide the aircraft with a quick take-off capability, reaching the desired interception altitude, while then achieving Mach 2 speeds to reach the target area. Once in range of radar, attack would commence with beam-riding missiles. To offset the expected onboard workload (now involving piloting, weapons management, and radar management), a crew of two was a must. In turn, this required a pressurized cockpit as well as ejection seats.

Authorities called for a finalized design no later than January 1962, which placed expediency at the forefront above all else.

de Havilland engineers attempted to meet the requirement through their DH.117 submission. It was, rather optimistically, intended that the aircraft could see its first-flight before the end of 1958 and Initial Operational Capability (IOC) could be reached within the intended 1962 timeframe. Up to four flyable aircraft would be constructed for the prototyping and flight-testing phases followed by production-quality units to take into active service.

While the official requirement called for a maximum speed in the vicinity of Mach 2, engineers saw their sleek aircraft flying in excess of Mach 2.3 and was also marketed with a service ceiling of 60,000 feet. Range would be augmented by the addition of wing tip fuel tanks to bolster the already-onboard fuel stores while under full war load. Due to the high speed involved, titanium would factor into the aircraft's overall construction to go along with lightweight, yet strong, alloys.

The DH.177, as proposed, incorporated tapered, straight-edged wing mainplanes low-mounted at midships along the fuselage sides. The mainplanes, made as slim as possible for limited drag, were given noticeable anhedral (downward angle) and were capped by the wing tip tanks. Each member would also feature a single underwing hardpoint to carry an AAM (at this point the "Blue Jay" series was in focus). The cockpit would seat its two crew in tandem aft of the long and slender nosecone housing the radar unit. The fuselage, also long and slender, tapered to a point under the single vertical tail fin. Along the midway span of the rudder were installed the horizontal tailplanes.

The engines were to be housed in nacelles formed into the lower fuselage sides, aspirated via semi-circular ports near the cockpit walls and exhausted through circular ports ahead of the tail unit. To benefit climb and straightline performance, a Spectre Spe.5 booster rocket of 11,000lb thrust was to be embedded into the ventral line of the fuselage. The engines-of-choice became de Havilland's own Gyron Junior afterning turbojets of 12,000lb thrust. Maximum estimated speed was officially Mach 2.35 at altitude.

As drawn up, the DH.117 had an overall length of 68.9 feet with a wingspan of 38 feet. Gross weight was 55,000lb.

Despite the British need and promising scope of the de Havilland proposal, the DH.117 was not to be. A mock-up was completed by de Havilland but little else was had for the project. It went on to join many other abandoned interceptor forms of the period as requirements changed and technology progressed.

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Power & Performance
Those special qualities that separate one aircraft design from another. Performance specifications presented assume optimal operating conditions for the de Havilland DH.117 Mach 2 High-Altitude Interceptor Proposal.
2 x de Havilland Gyron Junior afterburning (reheat) turbojet engines developing 12,000lb of thrust with 1 x Spectre Spe.5 rocket booster developing 10,000lb of additional thrust.
1,802 mph
2,900 kph | 1,566 kts
Max Speed
60,039 ft
18,300 m | 11 miles
Service Ceiling
621 miles
1,000 km | 540 nm
Operational Range
36,800 ft/min
11,217 m/min
City-to-City Ranges
Operational range when compared to distances between major cities (in KM).
The nose-to-tail, wingtip-to-wingtip physical qualities of the de Havilland DH.117 Mach 2 High-Altitude Interceptor Proposal.
66.8 ft
20.35 m
O/A Length
38.1 ft
(11.60 m)
O/A Width
55,116 lb
(25,000 kg)
Design Balance
The three qualities reflected below are altitude, speed, and range. The more full the box, the more balanced the design.
Available supported armament and special-mission equipment featured in the design of the de Havilland DH.117 Mach 2 High-Altitude Interceptor Proposal .
2 x Underwing hardpoints (one per wing) for the carrying of Blue Jay Mk.4 (Blue Vesta) air-to-air missiles (AAMs).
Notable series variants as part of the de Havilland DH.117 family line.
DH.117 - Base Project Designation.
Global customers who have evaluated and/or operated the de Havilland DH.117. Nations are displayed by flag, each linked to their respective national aircraft listing.

Total Production: 0 Units

Contractor(s): de Havilland Aircraft - UK
National flag of the United Kingdom

[ United Kingdom (cancelled) ]
Relative Max Speed
Hi: 1900mph
Lo: 950mph
Aircraft Max Listed Speed (1,802mph).

Graph Average of 1,425 MPH.
Era Crossover
Pie graph section
Showcasing Aircraft Era Crossover (if any)
Max Alt Visualization
Small airplane graphic
MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030
Aviation Timeline
1 / 1
Image of the de Havilland DH.117
Image copyright www.MilitaryFactory.com; No Reproduction Permitted.

Mission Roles
Some designs are single-minded in their approach while others offer a more versatile solution to airborne requirements.
Some designs stand the test of time while others are doomed to never advance beyond the drawing board; let history be their judge.
Going Further...
The de Havilland DH.117 Mach 2 High-Altitude Interceptor Proposal appears in the following collections:
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