No, The F-35B Does Not Use Afterburner In Vertical Landing Mode
Imagery of F-35Bs operating at night make it look like afterburner is used in vertical mode, but the truth is more interesting.
An F-35B stealth fighter conducting vertical or rolling vertical landings on a warship’s deck at night is a sight to behold. Perhaps the most dramatic aspect of this audio-visual spectacle is the vertical ‘pillar of thrust’ upon which the jet perches as it makes its descent onto the deck. But while it looks very much like an afterburner plume, and many on social media think that's what it is, the F-35B doesn’t actually engage this function when operating in vertical mode.
The effect, as seen in the photo at the top of this story — showing an F-35B on the U.K. Royal Navy carrier HMS Prince of Wales — is produced when a highly sensitive low-light camera picks up the very hot gas that’s pumped out of the F-35B’s rear nozzle upon landing at night.
A quick aside on afterburners to get everyone up to speed. Many high-performance military aircraft, the F-35B included, feature them. They inject fuel into a combustor in the jet pipe behind the turbine, for a significant boost in thrust when required, albeit at the cost of drastically increased fuel consumption and infrared signature.
We know, of course, that the F-35B’s engine already produces a lot of heat. In the past, the deck coatings and some structural elements of ships have had to be modified to deal with it. Even without the afterburner, the Pratt & Whitney F135 engine generates a staggering amount of thrust for the short takeoff and vertical landing (STOVL) operations that are unique to the F-35B variant of the aircraft.
A video shows a U.S. Marine Corps test pilot performing the first night-time vertical landing by an F-35B aboard the USS Wasp on August 14, 2013:
The War Zone spoke to one experienced former F-35B pilot, who prefers to remain anonymous, to get a better understanding of the technologies — and performance — involved in STOVL operations.
First off, the pilot gave us an idea of the sheer amount of thrust that we are dealing with in STOVL mode.
The variant of the F135 engine used in the F-35B, in dry thrust (without gas-guzzling afterburner engaged), develops around 18,500 pounds of thrust when in STOVL mode. It’s this hot gas that can be seen in the above images and others like it. The vectoring exhaust in the F-35B version is known as the 3 Bearing Swivel Nozzle or 3BSN. While the pilot can select separate stages (zones) of afterburner for a major thrust gain in conventional flight mode, it’s much harder to modulate finely for the more delicate STOVL operations.
At the same time, for STOVL operations, the F-35B is equipped with a Rolls-Royce Lift Fan, a 50-inch, two-stage counter-rotating fan driven via a shaft from the main engine. The Lift Fan produces a similar amount of thrust — so, roughly another 18,500 pounds.
On top of this, add the two roll posts — which stream more hot exhaust gases from the main engine for additional stability — generating between 1,800 pounds and 2,000 pounds of thrust each.
All this makes for a little over 40,000 pounds of total thrust. Without afterburner.
“There’s a reserve to allow the jet to automatically tune it up over the life of the engine to keep it at that level,” the pilot explains. “That said, there are issues with the predicted life/fatigue already. So a new engine update is inbound.” You can read more about those plans here.
When hovering, the F-35B’s maximum weight is limited to 38,850 pounds to ensure there’s some extra thrust to provide flexibility and cushion the landing.
Less obvious, perhaps, is the work of the flight control system to manage the jet’s transition into vertical mode and then help put it safely on the deck.
“Decelerating into the hover, the aircraft is around 11 degrees nose-up,” the pilot continues. “As the aircraft goes into the jet-borne (JB) regime, the attitude changes progressively down to 1.8 degrees nose-up. So quite a change as you slow down — this is all controlled by the thrust split between the 3 Bearing Swivel Nozzle (3BSN) at the back and the Lift Fan. Then, as the pilot commands a descent from the hover down to the pad, the thrust split increases the attitude from 1.8 to 3.8 degrees nose-up to account for sloping pads or a pitching deck, ensuring the main wheels touch down before the nose wheel.”
The opposite then happens when the pilot commands the F-35B to accelerate out of the hover and into the conventional flight mode. “[The jet] starts at 1.8 degrees nose-up and as you go into semi-jet borne flight around 60 KCAS [Knots Calibrated Airspeed], the attitude raises to 11 degrees nose-up to make the wing take some of the lift load and lower the amount of engine thrust required by the Lift Fan and 3BSN combination in the vertical axis. Eventually, the Lift Fan thrust is reduced, and a speed is achieved that allows the aircraft to be converted out of STOVL mode and into CTOL [conventional takeoff and landing] mode as a conventional fixed-wing fighter.”
“It’s astoundingly clever,” the pilot enthuses.
Cleverer still is a variation of the vertical recovery that’s seen in the photo at the top of this story — the Shipborne Rolling Vertical Landing (SRVL), a concept you can read more about here and here.
A standard F-35B recovery involves the jet being brought alongside the ship in a hover, translating sideways over the deck, before gently lowering to land. The advantage of this maneuver is increased safety, due to the low speeds involved, with no need to decelerate to a stop using the brakes.
In contrast, the SRVL makes use of a combination of powered and wing-borne lift to make a rolling landing, with the F-35B then brought to a stop using its brakes. According to the Royal Navy, “An SRVL uses a different approach, with the jet using a more conventional landing pattern, approaching the ship from the aft end, at speed, using the thrust from the nozzle and lift created by air over the wings to touch down and come to a stop as soon as possible.”
A video from the Shipborne Rolling Vertical Landing simulator at the BAE Warton facility in the United Kingdom:
The main advantage of an SRVL is that the F-35B can return to the ship with a heavier load of fuel and/or weapons. Otherwise, expensive stores might have to be ejected into the sea if they are not expended. It’s hoped that the SRVL maneuver will allow the F-35B to land back on the ship with a payload gain of 2,000 pounds, equivalent to four Paveway IV precision-guided bombs.
The SRVL concept was proven by test pilots aboard the aircraft carrier HMS Queen Elizabeth in 2018. The photo at the top of this story was taken during trials aboard sister carrier HMS Prince of Wales in October 2023, which were aimed to introduce the SRVL capability to frontline pilots.
Achieving an SRVL requires close cooperation between the pilot and the ship’s landing signal officer (LSO) in the flying control office. The pilot also receives flightpath cues from their helmet-mounted display.
Meanwhile, the Prince of Wales features a visual landing aid — known as the Bedford Array — specifically tailored to SRVLs. This comprises an array of lights in the flight deck tramlines, which indicates the glideslope to the pilot.
Currently, the United Kingdom is the only F-35B operator committed to introducing the SRVL to its concept of operations, although the U.S. Marine Corps has shown some interest in the past. Still, this is likely connected with operations from British aircraft carriers rather than U.S. Navy amphibious assault ships. Regardless, the U.S. Marine Corps continues to be involved in the trials with the Royal Navy, as part of the Integrated Test Force. SRVLs may well also be of relevance to Italy and Japan, both of which also operate their F-35Bs from ships, but just how safe it would be on those ships's smaller decks is unclear at this time.
Whether by day or night, returning an F-35B to the deck of a ship showcases some extremely sophisticated technology, some of it more visible than others. While a nighttime recovery may suggest the use of afterburner, the truth is, if anything, more impressive, with the jet being brought back to the ship thanks to roughly 40,000 pounds of non-afterburning thrust.
Contact the author: thomas@thedrive.com
