In 1956, Vickers had performed a series of low level tests in WZ383 to assess the type for low level flight at high speed.
Several modifications to the aircraft were made, including a metal radome, debris guards on the two inboard engines, and after six flights the aileron and elevator artificial feel was reduced by 50%.
Pilots reported problems with cabin heating and condensation that would need remedying.
The aircraft was fitted with data recording equipment and these data were used by Vickers to estimate the remaining safe life of the type under these flying conditions.
Initially a safe life of 75 hours was recommended, which became "the real figure might be less than 200 hours".
The number of hours flown by each Valiant in a year was an operational issue for the RAF.

Later the RAE ran a similar series of tests that more closely resembled actual operational conditions including low level and taxiing; the corresponding report published in 1958 produced data that could be used to get a better grasp on which flight conditions produced the most damage, and enable a better projection of the future life span for the type.

In May 1957 Flight reported an "incident at Boscombe Down, when a Valiant rear spar was damaged after a rocket-assisted takeoff at overload weight (the reason for the rocket-assistance)" This aircraft was the second prototype WB 215; it was subsequently broken up for wing fatigue testing after it had flown 489 hours.

After years of front-line service, in July 1964, a cracked spar was found in one of the three Valiants (either WZ394 – Wynne, or WZ389 – Morgan) on Operation Pontifex.
This was followed on 6 August by a failure of the starboard wing rear spar at 30,000 ft, in WP217, an OCU aircraft from Gaydon captained by Flight Lieutenant "Taffy" Foreman.
The aircraft landed back at Gaydon but without flap deployment because damage to the starboard rear spar caused the flap rollers to come out of their guides so that the flap would not lower on that side.
Later inspection of the aircraft also showed the fuselage skin below the starboard inner plane had buckled, popping the rivets; the engine door had cracked and the rivets had been pulled and the skin buckled on the top surface of the mainplane between the two engines.
Both of these aircraft were PR variants.

Inspections of the entire fleet showed that the wing spars were suffering from fatigue at between 35% and 75% of the assessed safe fatigue life, probably due to low level turbulence.
After this inspection, the aircraft were divided into three categories, Cat A aircraft continuing to fly, Cat B to fly to a repair base, and Cat C requiring repair before flying again.
The tanker squadrons had the highest proportion of Cat A aircraft because their role had been mainly at high level.
This also caused the methods of assessing fatigue lives to be reviewed.
By the time the type was scrapped, only about 50 aircraft were still in service; the rest had been slowly accumulating at various RAF Maintenance Units designated as "Non effective Aircraft".

Initially there was no question of retiring the type, or even a majority of affected aircraft.
Repairs were actively taking place at Valiant bases such as Marham using working parties from Vickers plus RAF technicians from the base.
 In January 1965, the Wilson government with Denis Healey as Secretary of State for Defence decided that the expense of the repairs could not be justified, given the short operational life left to the Valiant, and the fleet was permanently grounded as of 26 January 1965.
The QRA alert that had been in place for SACEUR was maintained until the final grounding.
When asked to make a statement regarding the Valiant's scrapping in the House of Commons, Denis Healey stated that it "was not in any way connected with low-level flying" and that the "last Government took the decision to continue operating the Valiant force for another four years after its planned fatigue life was complete".

Aviation author Barry Jones commented in his book that: "A question has to be asked.
For two years before the d
In 1956, Vickers had performed a series of low level tests in WZ383 to assess the type for low level flight at high speed. Several modifications to the aircraft were made, including a metal radome, debris guards on the two inboard engines, and after six flights the aileron and elevator artificial feel was reduced by 50%. Pilots reported problems with cabin heating and condensation that would need remedying. The aircraft was fitted with data recording equipment and these data were used by Vickers to estimate the remaining safe life of the type under these flying conditions. Initially a safe life of 75 hours was recommended, which became "the real figure might be less than 200 hours". The number of hours flown by each Valiant in a year was an operational issue for the RAF.
Later the RAE ran a similar series of tests that more closely resembled actual operational conditions including low level and taxiing; the corresponding report published in 1958 produced data that could be used to get a better grasp on which flight conditions produced the most damage, and enable a better projection of the future life span for the type.
In May 1957 Flight reported an "incident at Boscombe Down, when a Valiant rear spar was damaged after a rocket-assisted takeoff at overload weight (the reason for the rocket-assistance)" This aircraft was the second prototype WB 215; it was subsequently broken up for wing fatigue testing after it had flown 489 hours. 
After years of front-line service, in July 1964, a cracked spar was found in one of the three Valiants (either WZ394 – Wynne, or WZ389 – Morgan) on Operation Pontifex. This was followed on 6 August by a failure of the starboard wing rear spar at 30,000 ft, in WP217, an OCU aircraft from Gaydon captained by Flight Lieutenant "Taffy" Foreman. The aircraft landed back at Gaydon but without flap deployment because damage to the starboard rear spar caused the flap rollers to come out of their guides so that the flap would not lower on that side. Later inspection of the aircraft also showed the fuselage skin below the starboard inner plane had buckled, popping the rivets; the engine door had cracked and the rivets had been pulled and the skin buckled on the top surface of the mainplane between the two engines. Both of these aircraft were PR variants.
Inspections of the entire fleet showed that the wing spars were suffering from fatigue at between 35% and 75% of the assessed safe fatigue life, probably due to low level turbulence. After this inspection, the aircraft were divided into three categories, Cat A aircraft continuing to fly, Cat B to fly to a repair base, and Cat C requiring repair before flying again. The tanker squadrons had the highest proportion of Cat A aircraft because their role had been mainly at high level. This also caused the methods of assessing fatigue lives to be reviewed. By the time the type was scrapped, only about 50 aircraft were still in service; the rest had been slowly accumulating at various RAF Maintenance Units designated as "Non effective Aircraft".
Initially there was no question of retiring the type, or even a majority of affected aircraft. Repairs were actively taking place at Valiant bases such as Marham using working parties from Vickers plus RAF technicians from the base.  In January 1965, the Wilson government with Denis Healey as Secretary of State for Defence decided that the expense of the repairs could not be justified, given the short operational life left to the Valiant, and the fleet was permanently grounded as of 26 January 1965. The QRA alert that had been in place for SACEUR was maintained until the final grounding. When asked to make a statement regarding the Valiant's scrapping in the House of Commons, Denis Healey stated that it "was not in any way connected with low-level flying" and that the "last Government took the decision to continue operating the Valiant force for another four years after its planned fatigue life was complete".
Aviation author Barry Jones commented in his book that: "A question has to be asked. For two years before the d
Vickers Valiant