Editing Hawker Typhoon (section)

===Long-range fighter and fighter-bomber===
[[File:Hawker Typhoon 3 ExCC.jpg|thumb|Early production Typhoon with 45-gallon drop tanks and unfaired cannon; the shallow gull shape of the wing can be seen in this view.]]
From early 1943 the wings were plumbed and adapted to carry cylindrical {{convert|45|impgal|adj=on|abbr=on}} [[drop tank]]s,{{refn|These same drop tanks used by the Hurricane from 1940.|group=nb}} increasing the Typhoon's range from {{convert|690|nmi|km}} to up to {{convert|1,090|nmi|km}}. This enabled Typhoons to range deep into France, the Netherlands and Belgium. Some units, such as 609 Squadron and [[No. 198 Squadron RAF|198 Squadron]], were able to achieve notable success in air combat and ground attack operations using these long-range Typhoons.<ref name="Thomas and Shores 1988, p. 25.">Thomas and Shores 1988, p. 25.</ref>

As production continued, the Typhoon's role changed from a low-level interceptor fighter to a fighter bomber. Racks capable of carrying {{convert|500|lb|adj=on}} bombs were fitted to the wings from October 1942 and were first used operationally by [[No. 181 Squadron RAF|181 Squadron]]. By mid-1943, all Typhoons off the production line were capable of carrying bombs. Bigger, solid rubber, grooved "anti-shimmy" tail wheel tyres were introduced in March 1943 on all Typhoons from the 1,001st production aircraft, ''EK238''. The new tyres helped to make heavier, bomb-laden Typhoons more manageable during ground manoeuvres. With the introduction of the bomb racks, small extensions were added to the cannon shell case ejector slots. These allowed the casings to drop clear of bombs or drop tanks suspended from the wing racks.<ref name="Thomas and Shores 1988, p. 23">Thomas and Shores 1988, p. 23.</ref> Because of the vulnerability of the Typhoon's [[Water cooling|liquid-cooled engine]] cooling system to ground fire, some {{convert|780|lb}} of armour was added, lining the sides and bottom of the cockpit and engine compartments, as well as the [[radiator (engine cooling)|radiator]] bath.<ref>Thomas 2010, p. 11.</ref>

With the added weight of the bombs and armour, bigger [[disc brake|brake discs]] were fitted to the main wheels. At first this only applied to "Bombphoons", but eventually all Typhoons used these brakes. After tests conducted in 1943, it was determined that the Typhoon was capable of carrying a {{convert|1000|lb|adj=on}} bomb under each wing. With the increased load, it was decided that the extra take-off performance conferred by a four-bladed propeller was an advantage. This led to the adoption of a four-bladed propeller unit (de Havilland or [[Rotol]]) from early 1944. Coinciding with the new propeller, it was also decided that the larger tailplanes of the [[Hawker Tempest]] were to be fitted when tests showed that they improved the handling characteristics of the Typhoon when carrying {{convert|1000|lb|adj=on}} bombs.<ref name="Bentley 1975, p. 542.">Bentley 1975, p. 542.</ref><ref>Thomas and Shores 1988, pp. 23, 24.</ref> Problems were experienced with oil seal leaks from the new propeller unit and a growing number of Typhoons were held in Maintenance Units (MUs) awaiting the arrival of new seals from the U.S. Some 200 Typhoons were manufactured with the new Tempest tails and the three-bladed propeller. A modification programme was inaugurated but it took several months before a majority of operational Typhoons had the four-bladed propeller and enlarged tailplane.<ref>Thomas 2010, p. 15.</ref>{{refn|Early in its service life, the Typhoon airframe was prone to a high-frequency vibration while in flight, such that pilots reported that touching the cockpit walls was akin to receiving a mild electric shock.<ref>Thomas and Shores 1988, pp. 21, 23.</ref> Although not dangerous, it was uncomfortable, and a specially sprung seat was designed and fitted. With the introduction of the four-bladed propeller and larger tailplane it was found that not only was the performance and handling of the Typhoon enhanced, the vibration was much reduced.<ref name="Thos0912">Thomas 2010, p. 12.</ref>|group=nb}}

In June 1943, Hawker fitted a Typhoon with four steel "Mark I" rocket rails under each wing. Trials at the [[Aeroplane and Armament Experimental Establishment]] (A & AEE) and [[Air Fighting Development Unit]] (AFDU) showed that the combination of the [[RP-3]] rocket and the stable, high-speed platform of the Typhoon was promising. Carrying the eight rails and rockets, it was found that the top speed was reduced by {{convert|38|mph|abbr=on}}, with no adverse handling effects. As a result, the Mk I rails and RP-3s were first fitted to production aircraft of [[No. 181 Squadron RAF|181 Squadron]] in October 1943.<ref>Thomas 2010, pp. 13, 46.</ref> At first attempts were made to arm Typhoons with either bombs or rockets depending on requirements but it was soon decided that squadrons would specialise. By [[D-Day]], the 2nd TAF was able to field 11 RP ("Rockphoon") Typhoon squadrons and seven "Bombphoon" squadrons.<ref>Thomas 2010, pp. 16, 58, 88–90.</ref>

Later in 1944, attempts were made to increase the firepower by "double banking" rockets on each rail, enabling the Typhoon to carry 16 rockets. The problems involved in operating Typhoons from 2nd TAF airstrips meant that this was not much used, although some Typhoons did fly operationally with 12 rockets, using double-banked rockets on the inner rails.<ref>Thomas 2000, p. 25.</ref> When extra range was required, Typhoons could also operate carrying a drop tank and two rockets outboard of the tank under each wing. From December 1944, aluminium "Mark III" rails, which weighed {{convert|240|lb}} per set, replaced the steel Mk Is, which weighed {{convert|480|lb}}.<ref name="Thomas and Shores 1988, pp. 25-26.">Thomas and Shores 1988, pp. 25–26.</ref>{{refn|Starting in June 1944, new production Typhoons had the landing light in the leading edge of the port wing, although most units of 2 TAF omitted this feature and faired over the opening with a metal panel, giving the appearance that all production Typhoons were manufactured without the lights.<ref>Thomas 2010, p. 20.</ref>|group=nb}}

In late 1943, Mk III IFF replaced the Mk I and the tailplane tip to fuselage [[Identification friend or foe]] (IFF) aerials were replaced by a "[[bayonet]]" aerial under the wing's centre section. A [[Beam Approach Beacon System]] (''Rebecca'') transponder unit was fitted in 1944, with the associated aerial appearing under the centre section.{{Cn|date=March 2024}}

Once Typhoons started operating from forward landing grounds in Normandy, it was found that the dust clouds stirred up by propeller wash consisted of over 80 percent of hard, abrasive material which was damaging the Sabre engines. The [[sleeve valve]]s in particular were subject to excessive wear and it was calculated that engines would last for three take-offs. As a result, a "dome deflector" was designed and manufactured at great speed by Napier, and within a week most Typhoons had been fitted with it. In operational service these mushroom-shaped [[air filter]]s, which became red hot, had a propensity for being blown off the air intake at high speed whenever a Sabre engine backfired. They were soon replaced by drum-shaped filters designed by the [[Royal Aircraft Establishment|RAE]] and Vokes. These had "[[cuckoo clock]]" doors in front, which swung open with the pressure changes caused by engine backfires. This standardised filter became Typhoon Mod.420.<ref name="Shores and Thomas 2008, p.602.">Shores and Thomas 2008, p. 602.</ref>

At the end of June 1944, a decision was taken to fit tropical air filters as standard, similar to those fitted to the three Typhoons which had been sent to North Africa in 1943. One thousand sets of the filters were to be manufactured and fitted to front line Typhoons as Mod. 421. It was estimated that these could be fitted to all Typhoons on the production lines by the end of September. Research shows that late Typhoons starting in the ''RB---'' series were fitted with the filters, as were some rebuilt aircraft from earlier production batches. Mod. 421 appeared as a streamlined rectangular "hump", just behind the main radiator fairing and between the inner wheel doors, where the [[carburetor|updraught carburettor]] intake was located.<ref name="Shores and Thomas 2008, p.602."/>

A small, elongated oval [[Pitot-static system|static port]] appeared on the rear starboard fuselage in late 1944. This was apparently used to more accurately measure the aircraft's altitude.

[[File:Hawker Typhoon ExCC.jpg|thumb|A late production Typhoon with full RP-3 armament, a mix of SAP/HE 60 lb warheads and HE fragmentation head.<ref>Thomas 2010, pp. 13–14.</ref>]]

One Typhoon, ''R8694'', was used by [[D. Napier & Son|Napier]] for trials with the more powerful Sabre IV, cooled using an annular radiator and driving a four-bladed propeller. The new engine and radiator arrangement required substantial modifications to the forward fuselage and engine bearer structures. Although a maximum speed of {{convert|452|mph|km/h|abbr=on}} was claimed by Napier, it was decided that the modifications would not be worthwhile, mainly because of the promising development of the Tempest, and because the disruption to Typhoon production would not be sufficiently outweighed by any benefit achieved.<ref>Thomas and Shores 1988, pp. 20–21.</ref><ref>[http://www.napierheritage.org.uk/spip.php?article100438 "Napier Power Heritage."] {{webarchive|url=https://web.archive.org/web/20090212123126/http://www.napierheritage.org.uk/spip.php?article100438 |date=12 February 2009 }} ''napierheritage.org.'' Retrieved: 31 July 2011.</ref>