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de Havilland DH.108 (Swallow)

Jet-Powered, Swept-Wing Research Aircraft [ 1946 ]

All three completed and flown DH.108 Swallow test aircraft claimed the lives of three pilots - such was its stained career in the air.

Authored By: Staff Writer | Last Edited: 06/05/2018 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The elegant - though highly lethal - de Havilland DH.108 "Swallow" was one of the more important research aircraft for British aviation during the 1940s and early 1950s. Not designed nor developed to any specific military fighter requirement, the aircraft actually existed researching supersonic flight and sweptback wings in regards to the de Havilland DH.106 "Comet" jet passenger airliner program. The Comet became the world's first jet airliner but its own issues limited its overall reach - allowing competitors to claim a large portion of the market share. The research-oriented DH.108 was, itself, a dangerous plane to fly for it claimed the lives of three test pilots in separate aircraft losses, forever staining the Swallow program. Despite the unfortunate setbacks, the DH.108 proved critical in advancing British understanding of swept-back wings, jet-powered flight, and supersonic speeds and control.

The Comet airliner was a program being championed by British authorities in the latter years of World War 2 in an effort provide local aero industry with commitments well after the fighting had ceased. The Comet would be a passenger-minded, turbojet-powered design utilizing a tailless configuration and an advanced sweptback monoplane wing assembly. The charge fell to the storied concern of de Havilland which used its DH.108 platform as the starting point for the finalized research aircraft. The dimensionally smaller, single-seat airframe would mimic many of the qualities to be found in the full-sized Comet and serve to test the various control conditions at supersonic speeds. The Air Ministry requested a pair of prototypes while the name of "Swallow" was only attached to the aircraft by the Ministry of Supply and never official adopted.

The de Havilland DH.108 research aircraft was formed from the body of the existing de Havilland DH.100 "Vampire" (F.Mk 1model), a jet-powered, single-seat fighter-bomber seeing service entry in 1946. The aircraft featured a centralized nacelle housing cockpit and powerplant with a monoplane wing arrangement held to either side of the fuselage. A twin-boom configuration was used to make up the tail section and this produced a twin vertical tail fin arrangement which attached via a single horizontal tailplane assembly between them. When adopted into service, the Vampire became Britain's second jet-powered fighter following the classic Gloster "Meteor".

The choice to modify an existing aircraft expedited the development process. The Vampire F.Mk 1 saw its twin tailbooms deleted which also meant that the vertical tail fins and stabilizer were lost. The cockpit nacelle and engine installation remained as in the original though the nacelle was lengthened some to accommodate a new single vertical tail fin mounted over the jetpipe. The wings were the true addition, specially-designed assemblies which featured 43-degree sweepback and installed in place of the original straight wings of the Vampire. The first aircraft in the Swallow line was known as "TG283" and recorded its first flight on May 15th, 1946 with Geoffrey de Havilland, Jr. - son of the famous company founder - at the controls. Power was from a de Havilland Goblin 2 engine of 3,100lb thrust.

Additional testing revealed a slew of issues under specific conditions, proving the aircraft a handful for even the most veteran of pilots. To help offset difficulties in ground running and landing, the undercarriage of the "Sea Vampire" - the navalized variant of the land-based Vampire - was installed. Its career in the air war short-lived for it was during a stall trial on May 1st, 1950 that the aircraft entered into a spin and was lost, killing the test pilot. During its time aloft, TG283 managed a maximum speed of approximately 350 miles per hour.©MilitaryFactory.com
TG306 became the second aircraft of the triad and this version introduced retractable slats over the fixed, wooden Handley-Page slats featured on TG283. Power was served through a de Havilland Goblin 4 turbojet of 3,500lbs thrust. Its first flight came during June of 1946 and improved performance led to the aircraft attempting to break the World Air Speed record (held by the competing Gloster Meteor at 616mph). TG283 was met with a few adjustments for the attempt but a trial flight prior ended with the aircraft losing control once more, breaking up in mid-flight, and killing pilot Geoffrey de Havilland, Jr. on September, 27th, 1946. During its time in the air, TG283 recorded a maximum speed of 580 miles per hour - though this achieved in a dive.

The DH.108 program then introduced the final flying machine as VW120 - largely influenced by the TG306 model and its issues. First flight was on July 24th, 1947 and the design now boasted an ejection seat for the pilot and a revised cockpit and forward fuselage. Additional strengthening was added to the structure to help avoid the pitfalls of the previous mark in the series. Power-assisted wing surfaces and controls attempted to take some of the fatigue from the pilot. Power was now from a de Havilland Goblin 5 turbojet engine of 3,600lbs thrust. The aircraft went on to become the first British-designed aircraft to break the sound barrier, this accomplished during a steep dive on September 6th, 1948 and resulting in the official speed of Mach 1.02 being recorded. During the dive, the pilot lost control of the aircraft but was able to reclaim her.

It was during another flight on February 15th, 1950 that VW120 was lost when it disintegrated in-flight. Despite access to an ejection seat, the pilot was lost with the aircraft and such ended the tumultuous DH.108 research program. The aircraft proved just as lethal as it was beautiful by 1940s standards, showcasing clean lines and a certain simplicity about her. While the Dh.106 Comet airliner was eventually brought online, it too suffered a stained record with the in-flight disintegrations of three aircraft. The losses and publicity no doubt damaged sales and companies like Boeing were all to ready to take up the market share. Despite this, the Comet - introduced in 1952 - managed a long service life if only through the 114 total examples completed. These served with a handful of carriers with the final Comet retired in March of 1997. The Comet also made up the basis of the RAF's Hawker Siddeley "Nimrod" maritime patrol platform - which itself was not retired until 2011.

The finalized Comet form was completed with a conventional tail unit fitting a sole vertical tail fin and low-set horizontal planes. It did, however, sport sweptback wing surfaces all the main and tailplane units and its engine intakes were similarly placed as on the Swallow design, well-contoured at the wingroots to appear as part of the wing assembly itself.©MilitaryFactory.com
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Service Year

United Kingdom national flag graphic
United Kingdom

Not in Service.


National flag of the United Kingdom United Kingdom (retired)
(OPERATORS list includes past, present, and future operators when applicable)
X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.

31.2 ft
(9.50 m)
39.0 ft
(11.89 m)
Empty Wgt
8,940 lb
(4,055 kg)
15,818 lb
(7,175 kg)
Wgt Diff
+6,878 lb
(+3,120 kg)
(Showcased structural values pertain to the de Havilland VW120 production variant)
Installed: 1 x de Havilland Goblin 5 turbojet engine developing 3,600lb of thrust.
Max Speed
677 mph
(1,090 kph | 589 kts)
35,433 ft
(10,800 m | 7 mi)
730 mi
(1,175 km | 2,176 nm)

♦ MACH Regime (Sonic)
RANGES (MPH) Subsonic: <614mph | Transonic: 614-921 | Supersonic: 921-3836 | Hypersonic: 3836-7673 | Hi-Hypersonic: 7673-19180 | Reentry: >19030

(Showcased performance specifications pertain to the de Havilland VW120 production variant. Performance specifications showcased above are subject to environmental factors as well as aircraft configuration. Estimates are made when Real Data not available. Compare this aircraft entry against any other in our database or View aircraft by powerplant type)

Supported Types

(Not all ordnance types may be represented in the showcase above)
DH.108 - de Havilland model designation
"Swallow" - Unofficial nickname
TG283 - First aircraft; wooden, full-span Handley-Page slats along leading wing edge.
TG306 - Second aircraft; retractable slats
VW120 - Third aircraft; ejection seat fitted; various improvements from TG306.

General Assessment
Values are derrived from a variety of categories related to the design, overall function, and historical influence of this aircraft in aviation history.
Overall Rating
The overall rating takes into account over 60 individual factors related to this aircraft entry.
Rating is out of a possible 100 points.
Relative Maximum Speed
Hi: 750mph
Lo: 375mph
This entry's maximum listed speed (677mph).

Graph average of 563 miles-per-hour.
City-to-City Ranges
de Havilland VW120 operational range when compared to distances between major cities (in KM).
Max Altitude Visualization
Small airplane graphic
Design Balance
The three qualities reflected above are altitude, speed, and range.
Aviation Era Span
Pie graph section
Showcasing era cross-over of this aircraft design.
Unit Production (3)
Compared against Ilyushin IL-2 (military) and Cessna 172 (civilian).

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Images Gallery

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Image of the de Havilland DH.108 (Swallow)
Image from the Public Domain.


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