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aeronewsline :: Accueil :: Histoire :: Aéronefs 1945 à 1955
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Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 14:49
Operational history
Early years
The [Vous devez être inscrit et connecté pour voir ce lien] operated B-47 Stratojets (B-47s, EB-47s, RB-47s and YRB-47s) from 1951 through 1965.
When B-47s began to be delivered to the Air Force, most crews were excited about getting their hands on the hot new bomber, an aircraft whose performance was closer to that of jet fighters of the period than SAC's extant [Vous devez être inscrit et connecté pour voir ce lien] bomber.
The B-47 was so fast that in the early days the aircraft set records with ease.
The aircraft handled well in flight, with a fighter-like light touch to the controls.
Early years
The [Vous devez être inscrit et connecté pour voir ce lien] operated B-47 Stratojets (B-47s, EB-47s, RB-47s and YRB-47s) from 1951 through 1965.
When B-47s began to be delivered to the Air Force, most crews were excited about getting their hands on the hot new bomber, an aircraft whose performance was closer to that of jet fighters of the period than SAC's extant [Vous devez être inscrit et connecté pour voir ce lien] bomber.
The B-47 was so fast that in the early days the aircraft set records with ease.
The aircraft handled well in flight, with a fighter-like light touch to the controls.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 14:55
It took the Air Force until 1953 to turn the B-47 into an operational aircraft.
The aircraft was sluggish on takeoff and too fast on landings, a very unpleasant combination.
If the pilot landed at the wrong angle, the aircraft would "porpoise", bouncing fore-and-aft.
If the pilot didn't lift off for another go-round, instability would quickly cause the bomber to skid onto one wing and cartwheel.
Because the wings and surfaces were flexible and bent in flight, low altitude speed restrictions were necessary to ensure effective flight control.
The aircraft was sluggish on takeoff and too fast on landings, a very unpleasant combination.
If the pilot landed at the wrong angle, the aircraft would "porpoise", bouncing fore-and-aft.
If the pilot didn't lift off for another go-round, instability would quickly cause the bomber to skid onto one wing and cartwheel.
Because the wings and surfaces were flexible and bent in flight, low altitude speed restrictions were necessary to ensure effective flight control.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 14:56
Improved training led to a good safety record, and few crews felt the aircraft was unsafe or too demanding, but apparently there were some aircrews who had little affection for the B-47.
Crew workload was high, with only three officer crew members to keep the B-47 flying right.
The [Vous devez être inscrit et connecté pour voir ce lien], in contrast, generally had six crewmen, 5 officers and 1 enlisted, with far more internal cabin space.
Crew workload was high, with only three officer crew members to keep the B-47 flying right.
The [Vous devez être inscrit et connecté pour voir ce lien], in contrast, generally had six crewmen, 5 officers and 1 enlisted, with far more internal cabin space.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 14:59
Training and problems
The B-47's reliability and serviceability were regarded as good.
The only major problem was poor avionics reliability, normal in this environment given the [Vous devez être inscrit et connecté pour voir ce lien] technology at the time, and the need to place some equipment outside the pressurized crew compartment.
Much work was done to improve avionics reliability, but they remained problematic throughout the B-47's operational life.
The B-47's reliability and serviceability were regarded as good.
The only major problem was poor avionics reliability, normal in this environment given the [Vous devez être inscrit et connecté pour voir ce lien] technology at the time, and the need to place some equipment outside the pressurized crew compartment.
Much work was done to improve avionics reliability, but they remained problematic throughout the B-47's operational life.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:03
Several models of the B-47 starting in 1950 included a fuel tank [Vous devez être inscrit et connecté pour voir ce lien], in which [Vous devez être inscrit et connecté pour voir ce lien] was sublimated into [Vous devez être inscrit et connecté pour voir ce lien] vapor while the fuel pumps operated or while the in-flight refueling system was in use.
The carbon dioxide was then pumped into the fuel tanks and the rest of the fuel system, ensuring that the amount of oxygen in the fuel system was low, and thereby reducing the probability of an explosion.
Ten carbon dioxide tanks and heaters were involved.
The system was implemented largely to reduce risks from [Vous devez être inscrit et connecté pour voir ce lien] discharges occurring during in-flight refueling.
The carbon dioxide was then pumped into the fuel tanks and the rest of the fuel system, ensuring that the amount of oxygen in the fuel system was low, and thereby reducing the probability of an explosion.
Ten carbon dioxide tanks and heaters were involved.
The system was implemented largely to reduce risks from [Vous devez être inscrit et connecté pour voir ce lien] discharges occurring during in-flight refueling.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:05
Initial mission profiles included the [Vous devez être inscrit et connecté pour voir ce lien] (Low Altitude Bombing System) of nuclear weapons.
As the training for this imposes repeated high stress, the airframe lifetime would have been severely limited by [Vous devez être inscrit et connecté pour voir ce lien], and this maneuver was eliminated.
As the training for this imposes repeated high stress, the airframe lifetime would have been severely limited by [Vous devez être inscrit et connecté pour voir ce lien], and this maneuver was eliminated.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:08
Prime years
By 1956, the U.S. Air Force had 28 wings of B-47 bombers and five wings of RB-47 reconnaissance aircraft.
The bombers were the first line of America's strategic nuclear deterrent, often operating from forward bases in the [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien],[Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], Greenland and [Vous devez être inscrit et connecté pour voir ce lien].
B-47 bombers were often set up on "one-third" alert, with a third of the operational aircraft available sitting on hardstands or an alert ramp adjacent to the runway, loaded with fuel and nuclear weapons, crews on standby, ready to attack the [Vous devez être inscrit et connecté pour voir ce lien] at short notice.
By 1956, the U.S. Air Force had 28 wings of B-47 bombers and five wings of RB-47 reconnaissance aircraft.
The bombers were the first line of America's strategic nuclear deterrent, often operating from forward bases in the [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien],[Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], Greenland and [Vous devez être inscrit et connecté pour voir ce lien].
B-47 bombers were often set up on "one-third" alert, with a third of the operational aircraft available sitting on hardstands or an alert ramp adjacent to the runway, loaded with fuel and nuclear weapons, crews on standby, ready to attack the [Vous devez être inscrit et connecté pour voir ce lien] at short notice.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:11
Crews were also trained to perform "minimum interval takeoffs (MITO)", with one bomber following the other into the air at intervals of as little as 15 seconds, to launch all bombers as fast as possible.
MITO could be hazardous, as the bombers left turbulence and, with first generation turbojet engines with [Vous devez être inscrit et connecté pour voir ce lien] systems, dense black smoke that blinded pilots in the following aircraft.
MITO could be hazardous, as the bombers left turbulence and, with first generation turbojet engines with [Vous devez être inscrit et connecté pour voir ce lien] systems, dense black smoke that blinded pilots in the following aircraft.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:13
B-47 bombers apparently performed training missions in which they penetrated Soviet airspace in numbers.
The facts behind these missions remain controversial, with some claiming that [Vous devez être inscrit et connecté pour voir ce lien] ordered them without presidential knowledge or approval.
The B-47 would be the backbone of SAC into 1959, when the [Vous devez être inscrit et connecté pour voir ce lien] began to assume nuclear alert duties and the
number of B-47 bomber wings started to be reduced.
B-47 production ceased in 1957, though modifications and rebuilds continued after that.
The facts behind these missions remain controversial, with some claiming that [Vous devez être inscrit et connecté pour voir ce lien] ordered them without presidential knowledge or approval.
The B-47 would be the backbone of SAC into 1959, when the [Vous devez être inscrit et connecté pour voir ce lien] began to assume nuclear alert duties and the
number of B-47 bomber wings started to be reduced.
B-47 production ceased in 1957, though modifications and rebuilds continued after that.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:14
Operational practice for B-47 bomber operations during this time went from high altitude bombing to low altitude strike, which was judged more likely to penetrate Soviet defenses.
Bomber crews were trained in "pop-up" attacks, coming in at low level at 425 knots (787 km/h) and then climbing abruptly near the target before releasing a nuclear weapon, and the similar "[Vous devez être inscrit et connecté pour voir ce lien]" procedure, in which the aircraft released the weapon while climbing, and then rolled away to depart the area before bomb detonation.
Bomber crews were trained in "pop-up" attacks, coming in at low level at 425 knots (787 km/h) and then climbing abruptly near the target before releasing a nuclear weapon, and the similar "[Vous devez être inscrit et connecté pour voir ce lien]" procedure, in which the aircraft released the weapon while climbing, and then rolled away to depart the area before bomb detonation.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:17
Later years
Stress and fatigue incurred in low altitude operations led to a number of wing failures and crashes and an extensive refit program was initiated in 1958 to strengthen the wing mountings.
The program was known as "Milk Bottle", named after the big connecting pins that were replaced in the wing roots.
Stress and fatigue incurred in low altitude operations led to a number of wing failures and crashes and an extensive refit program was initiated in 1958 to strengthen the wing mountings.
The program was known as "Milk Bottle", named after the big connecting pins that were replaced in the wing roots.
Choste- CLUB
- Messages : 408
Re: Boeing B-47 Stratojet
par Choste Mar 20 Avr 2010, 15:20
One of the more notable mishaps involving a B-47 occurred on 5 February 1958 near Savannah, Georgia, in the so-called [Vous devez être inscrit et connecté pour voir ce lien].
A B-47 based out of [Vous devez être inscrit et connecté pour voir ce lien], Florida was engaged in a simulated combat exercise with an [Vous devez être inscrit et connecté pour voir ce lien], the bomber simulating an attacking aircraft and the fighter a defender.
As was the practice at the time, the B-47 was carrying a single 7,600 lb (3,400 kg) Mark 15 thermonuclear weapon without its core.
During this exercise, the F-86 collided with the B-47.
A B-47 based out of [Vous devez être inscrit et connecté pour voir ce lien], Florida was engaged in a simulated combat exercise with an [Vous devez être inscrit et connecté pour voir ce lien], the bomber simulating an attacking aircraft and the fighter a defender.
As was the practice at the time, the B-47 was carrying a single 7,600 lb (3,400 kg) Mark 15 thermonuclear weapon without its core.
During this exercise, the F-86 collided with the B-47.
Choste- CLUB
- Messages : 408
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