The F-35B and its different thermal impact on flight decks compared to the Harrier II

The Harrier II is nearing the end of its operational life, being progressively replaced by the F-35B Lightning II.

The Marines' farewell to their Harrier IIs: Spain is now their oldest operator
A rare formation flight of an F-35B stealth fighter and two Harrier II Plus

This replacement has already been completed in the British Royal Navy and the United States Marine Corps and is underway in the Italian Navy. Currently, the only Harrier IIs without a replacement are those of the Spanish Navy, due to the current Spanish government's refusal to acquire the F-35B. Last Friday, the US Navy released an impressive video recorded on August 4th aboard the amphibious aircraft carrier USS Boxer, showing F-35B fighters from Marine Fighter Attack Squadron 122 (VMFA-122) "Werewolves" landing at night and displaying the intense jet of propulsion from their tilting nozzles, directed against the flight deck:

The temperature problem has been present since the first Harriers began operating on aircraft carrier flight decks. Until then, ships of this type had not had to withstand such direct thermal stress as that generated by the Harrier's exhaust nozzles. The solution was to reinforce the flight decks, as was done with the Spanish aircraft carrier "Dédalo" before it began operating the AV-8S Matador, the Spanish version of the AV-8A Harrier.

The same thing has happened with the F-35B, but on a larger scale. The nozzles of this aircraft generate more heat than those of the Harrier II, but the stealth fighter's engine has much greater thrust, which generates more thermal stress on the flight decks. In 2010, a US congressional advisor noted: "AV-8B and F-35B temperatures might be the same, but so far they haven’t shown anyone their data; plus, you have to look at it from the perspective of total kinetic energy of the engine thrust. AV-8B has a thrust rating of 23,000lbs, whereas an F-35B thrust rating is 41,000lbs. He’s comparing a cigar torch lighter to a blow torch."

In the past decade, the US Navy had problems with the F-35B and the MV-22 Osprey on its amphibious aircraft carriers, as both the tiltrotor and the short takeoff and vertical landing version of the F-35 overheated the flight decks. On January 15, 2014, the United States Naval Institute published: "The B variant of the F-35 is a short take-off and vertical landing (STOVL) aircraft that produces much more heat when it lands and takes off than the current AV-8B Harrier fighters currently flown off of big decks. Likewise, the exhaust heat from the nacelles of the Osprey has damaged flight decks in the past."

This temperature difference has necessitated some changes. Both the US and Italian navies have had to reinforce their aircraft carriers to operate the F-35B. Without these modifications, there was a risk that this stealth fighter could deform the flight deck with its exhaust jets. In the United States, a ceramic material called Thermion has been applied to the flight decks of ships operating the F-35B, but its installation is limited to the areas of the flight deck most subjected to the thermal stress generated by these aircraft, as can be seen above. If the Spanish Navy were to want to operate the F-35B someday on the amphibious aircraft carrier "Juan Carlos I," it would have to make modifications, provided the ship has the capacity to integrate the F-35B, since it was designed to operate the Harrier II.