STOVL is an acronym which stands for S
ff and V
anding. It refers to the characteristics of an aircraft
or an aircraft carrier
. It is pronounced "stow-vill" with a very short 'i', at least by all serving officers I have heard use it.
As stated, the aircraft is (if it's an adjective) or must be (if it's a requirement) able to take off in a short distance and land vertically. This differs from VTOL in that it is acceptable for the aircraft to be unable to take off vertically when loaded down with mission stores and/or fuel.
First, of course, we need to know what 'short' means. Fortunately, there is a NATO standard definition - and since NATO nations and armed forces are generally the ones who use the STOVL acronym, we can use that!
Short take-off and vertical landing aircraft (STOVL): Fixed-wing aircraft capable of clearing a 15 metres (50-foot) obstacle within 450 metres (1500 feet) of commencing take-off run, and capable of landing vertically. (NATO Glossary of Terms and Definitions - Document AAP-6(2007), page 2-S-7.)
One of the more confusing things about this term is that most aircraft which are capable of STOVL are, at least technically, capable of full VTOL operations. However, in most cases, these aircraft can only take off vertically with their load reduced - generally past the point of usefulness. As a result, they are operated as STOVL rather than VTOL in practice. Perhaps the most famous example in the NATO nations is the AV-8B Harrier 'Jump Jet.' Technically, this aircraft is a V/STOL aircraft, as it is technically capable of VTOL operations - but again, with any useful combat loadout, the Harrier must perform a rolling takeoff. More recent examples of aircraft intended for STOVL use include the V-22 Osprey and the F-35 Lightning II Joint Strike Fighter lift-fan ("B") variant.
STOVL Aircraft Carriers
STOVL aircraft carriers, as one might expect, are ships designed to support the operation of STOVL aircraft. They are distinct from other carrier types such as STOBAR or CATOBAR carriers. Generally, they have large flat flight decks, with a distinctive 'ski jump' ramp at the forward end. This ramp converts some of the forward velocity of launching aircraft to a vertical 'hop'. This lets them avoid the (dangerous) part of VTOL flight regimes where the engine thrust needs to be redirected rearward while the aircraft has zero or very little airflow over the wings to stabilize it.
There are several operating STOVL aircraft carriers. As of 2010:
- United Kingdom: The United Kingdom's Royal Navy operates two STOVL carriers (HMS Illustrious and HMS Ark Royal). The third member of that class, HMS Invincible, was decommissioned in 2005. Both presently operate Sea Harriers.
- India: India purchased the HMS Hermes in 1986 and recommissioned her as INS Viraat. She is expected to serve until 2019, and she too operates Sea Harriers as her fixed-wing aircraft.
- Italy: Italy maintains the Guiseppe Garibaldi and the Cavour. Both use Sea Harriers.
- Spain: Spain has the R11 Principe de Asturias and the L61 Juan Carlos, the latter commissioning in September 2010. Both operate Sea Harriers.
- Thailand: Thailand has the HTMS Chakri Naruebet which is based on the Spanish Principe de Asturias. She operates Matador aircraft (Aha!) ...which are, in fact, export versions of the AV-8A Sea Harrier resold by Spain. (awww.)
- The United States: Although all the ships officially typed 'aircraft carrier' in the U.S. Armed Forces are the CATOBAR carriers of the U.S. Navy, the story doesn't end there. The U.S. Navy also maintains 10 amphibious assault ships of the Wasp (LHD) and Tarawa (LHA) classes with flight decks and hangars, all of which operate Harrier jump jets in addition to their helicopter contingent. At around 40,000 tons displacement, these ships are in fact larger than most other navies' "aircraft carriers", despite being less than half the displacement of the U.S. supercarrier.
All manner of carrier forces are planned, building, and due to come online in the near future. Some of these will be STOVL carriers, especially if the United States manages to actually complete and sell the F-35 Lightning II
B variant, with its lift fan system, as Sea Harriers are no longer manufactured and are becoming a bit long in the tooth. China is apparently pursuing STOBAR
or even CATOBAR
carriers with a navalized Sukhoi SU-33
variant, but their final plans for the Varyag
Iron Noder 2010