F-101 Question
Thread Starter
Join Date: Dec 2010
Location: New York & California
Posts: 414
Likes: 0
Received 0 Likes
on
0 Posts
F-101 Question
I remember hearing that the F-101 had a tendency to pitch up with little to no provocation due to it's heavy wing-loading, wing design, and T-tail configuration.
According to this page: http://www.456fis.org/F-101.htm
I'm confused about what's being said here. Are they saying that the plane on takeoff with full fuel tanks with full flaps was near the pitch-up and stall-point? Or are they actually saying that they needed full flaps just to fly at high-altitude?
According to this page: http://www.456fis.org/F-101.htm
By mid-1956 the continued testing of the 29 F-101As which had been accepted by the USAF up to that time had turned up a number of structural, propulsion, aerodynamic, and armament problems. Perhaps the most serious of these was a tendency of the aircraft to pitch-up, a problem which was never fully corrected even after much effort. Brigadier General Robin Olds, who commanded a Voodoo wing, reported that it did not take very much to make a F-101A suddenly and without warning to go into pitch-up, even while cruising. The angle of attack needed to achieve lift with full flaps and drop tanks was very close to the pitch-up stall point, where the flow of air over the wings created a down flow over the tail slab. On January 10, 1956, Major Lonnie R. Moore, a Korean War ace with 10 kills to his credit, was killed in a F-101A pitch-up mishap at Eglin AFB, Florida.
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
2,000 hours on the CF-101 Voodoo from 1969 - 1982.
Yes, the Voodoo would pitch-up, but only if the critical angle of attack (AoA) was exceeded. Because of the swept wing and high T-tail, as AoA increased, the airflow would eventually strike the top of the T-tail, causing the aircraft to depart controlled flight in a pitch-up. In other words, if you exceed critical AoA for a given weight, speed etc, the aircraft would pitch-up just before it would stall. The same aerodynamic tendency of other swept wing/high T-tail aircraft such as the F-104 and the BAC-111, I believe.
Recovery was simple, if you had enough altitude. Deploy the drag-chute to force the nose down and the aircraft would pick up flying speed.
The simple way to avoid this was to just avoid exceeding critical AoA. We had a good AoA indicator and the aircraft had a number of pitch control systems (horn, pusher, RLS) that would normally keep you out of trouble (below critical AoA). But they could be fooled sometimes.
Lots of indicated airspeed was always good and that was absolutely no problem with the Voodoo with its great thrust-to weight ratio. The only problem on take-off was getting the nose gear up quickly enough after rotation as it would hang at around 290 KIAS. And on a cold day, you would be there just seconds after lift-off. In fact, we did not use afterburners below 0 degrees F as the thrust was just too hard on the engine mounts.
Flaps were used only for take-off & landing. Only two positions - full up or full down (45 degrees).
Yes, the Voodoo would pitch-up, but only if the critical angle of attack (AoA) was exceeded. Because of the swept wing and high T-tail, as AoA increased, the airflow would eventually strike the top of the T-tail, causing the aircraft to depart controlled flight in a pitch-up. In other words, if you exceed critical AoA for a given weight, speed etc, the aircraft would pitch-up just before it would stall. The same aerodynamic tendency of other swept wing/high T-tail aircraft such as the F-104 and the BAC-111, I believe.
Recovery was simple, if you had enough altitude. Deploy the drag-chute to force the nose down and the aircraft would pick up flying speed.
The simple way to avoid this was to just avoid exceeding critical AoA. We had a good AoA indicator and the aircraft had a number of pitch control systems (horn, pusher, RLS) that would normally keep you out of trouble (below critical AoA). But they could be fooled sometimes.
Lots of indicated airspeed was always good and that was absolutely no problem with the Voodoo with its great thrust-to weight ratio. The only problem on take-off was getting the nose gear up quickly enough after rotation as it would hang at around 290 KIAS. And on a cold day, you would be there just seconds after lift-off. In fact, we did not use afterburners below 0 degrees F as the thrust was just too hard on the engine mounts.
Flaps were used only for take-off & landing. Only two positions - full up or full down (45 degrees).
Last edited by TLB; 28th Jun 2011 at 21:47.
I don't own this space under my name. I should have leased it while I still could
Digressing,
One of my wife's relations was killed flying with the RCAF sometime around 1960-64. Legend has it that he was in an F104 over Niagra Falls. There is a list of pilot casualties from the F104 and he is not listed.
It is possible he may have been on the CF101 rather than the CF104. Is there a similar list for aircrew fatalities?
One of my wife's relations was killed flying with the RCAF sometime around 1960-64. Legend has it that he was in an F104 over Niagra Falls. There is a list of pilot casualties from the F104 and he is not listed.
It is possible he may have been on the CF101 rather than the CF104. Is there a similar list for aircrew fatalities?
Aviator Extraordinaire
Join Date: May 2000
Location: Oklahoma City, Oklahoma USA
Age: 76
Posts: 2,394
Likes: 0
Received 0 Likes
on
0 Posts
The only problem on take-off was getting the nose gear up quickly enough after rotation as it would hang at around 290 KIAS.
But not always.
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
It is possible he may have been on the CF101 rather than the CF104. Is there a similar list for aircrew fatalities?
Join Date: Oct 2006
Location: The Great Midwest
Posts: 245
Likes: 0
Received 0 Likes
on
0 Posts
During USAF test pilot school in April/May of 1979 I flew one flight in the F-101 which was a Canadian version as there were no active USAF F-101s at the time.
The F-101 had engines with “hard burner lights”; that is there afterburner (reheat) did not have stages where fuel was gradually added as is done on modern burners, rather the fuel was dumped into the afterburner at one time resulting in a fairly interesting controlled explosion. For those who have not had the opportunity to hear this, the resulting “bang” was very “manly” in nature and from the cockpit there was no doubt that the burners had lit. The F-101 had a really great rate of climb for its time and that was the most memorable thing about the performance. In the cockpit you could see the heritage that it passed on to the F-4 in terms of layout and controls.
The T-tail also had the characteristic of becoming effective much sooner that the stabilator on the F-4. With the F-4 you held the stick full back during the takeoff run and the aircraft slowly rotated as the speed approached takeoff speed. We had a Canadian pilot (flew with the Snow Birds before TPS) who tried full aft stick with the 101 and the aircraft over-rotated and scraped the engine burner cans on the runway. Realize that these aircraft had been fitted with the P&W J57-P-55 engines which had afterburners extending almost 8’ from the fuselage. Fortunately it was decided that it was just cosmetic damage or I would not have gotten my flight.
The F-101 had engines with “hard burner lights”; that is there afterburner (reheat) did not have stages where fuel was gradually added as is done on modern burners, rather the fuel was dumped into the afterburner at one time resulting in a fairly interesting controlled explosion. For those who have not had the opportunity to hear this, the resulting “bang” was very “manly” in nature and from the cockpit there was no doubt that the burners had lit. The F-101 had a really great rate of climb for its time and that was the most memorable thing about the performance. In the cockpit you could see the heritage that it passed on to the F-4 in terms of layout and controls.
The T-tail also had the characteristic of becoming effective much sooner that the stabilator on the F-4. With the F-4 you held the stick full back during the takeoff run and the aircraft slowly rotated as the speed approached takeoff speed. We had a Canadian pilot (flew with the Snow Birds before TPS) who tried full aft stick with the 101 and the aircraft over-rotated and scraped the engine burner cans on the runway. Realize that these aircraft had been fitted with the P&W J57-P-55 engines which had afterburners extending almost 8’ from the fuselage. Fortunately it was decided that it was just cosmetic damage or I would not have gotten my flight.
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
The T-tail also had the characteristic of becoming effective much sooner that the stabilator on the F-4. With the F-4 you held the stick full back during the takeoff run and the aircraft slowly rotated as the speed approached takeoff speed. We had a Canadian pilot (flew with the Snow Birds before TPS) who tried full aft stick with the 101 and the aircraft over-rotated and scraped the engine burner cans on the runway. Realize that these aircraft had been fitted with the P&W J57-P-55 engines which had afterburners extending almost 8’ from the fuselage. Fortunately it was decided that it was just cosmetic damage or I would not have gotten my flight.
Take-off in the Voodoo was dead simple (although it all would occur very quickly): release brakes - full throttles - select burners (boom boom) - about 155 KIAS ease back on the stick and raise the nose about 5 degrees - check forward and hold that attitude - and about 230 KIAS the aircraft would very gracefully leap into the sky. No yanking or banking required. Same thing on landing - full elevator control down to about 150 KIAS and also full aileron and rudder control down to about 80 KIAS. And then nose wheel steering. Too easy !
Join Date: Mar 2009
Location: Ottawa, Canada
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
The F-101 had a really great rate of climb for its time and that was the most memorable thing about the performance. In the cockpit you could see the heritage that it passed on to the F-4 in terms of layout and controls.
Totally agree ! These two aircraft were very clearly traditional McAir products. Very similar instrumentation, hydraulics & electronics systems. And they both adhered to the old McAir philosophy: build me a fuselage of any shape or size - now give me engines that will push it to 1,000 knots !
Join Date: Dec 2001
Location: Richmond Texas
Posts: 305
Likes: 0
Received 0 Likes
on
0 Posts
TLB might be able to comfirm this but the legend was that before moving the throttles to afterburner on a night mission, the pilot repeated the mantra "If I can't sleep, nobody's gonna". One does not forget the double bang!
After an excellent landing you can use the airplane again!
After an excellent landing you can use the airplane again!
Last edited by Flash2001; 29th Jun 2011 at 21:56.
Bentwaters
I remember in 1959 or 1960 going to the USAF Bentwaters airshow in RAF Uniform.
I hitched the few miles from RAF Bawdsey.
Being in uniform I had the run of the place.
I was invited to watch the show out in the midddle of the Airfield near a small comms. type building.
Memories of the High speed. low level afterburners on, "Crossover" by 4 F101 Voodoos.
The crossover point was the Building!!!!. Amazing.
Those were the days.
OPF
I hitched the few miles from RAF Bawdsey.
Being in uniform I had the run of the place.
I was invited to watch the show out in the midddle of the Airfield near a small comms. type building.
Memories of the High speed. low level afterburners on, "Crossover" by 4 F101 Voodoos.
The crossover point was the Building!!!!. Amazing.
Those were the days.
OPF
Aviator Extraordinaire
Join Date: May 2000
Location: Oklahoma City, Oklahoma USA
Age: 76
Posts: 2,394
Likes: 0
Received 0 Likes
on
0 Posts
I remember in 1959 or 1960 going to the USAF Bentwaters airshow in RAF Uniform
Back to the 101, I seem to remember that when the 101 first came out that both ABs lit at the same time, so rather than a Boom/Boom it was a single really large Boom. But then it was discovered that the wing spar was being damaged by the force of both ABs lighting at the same time and after that the ABs were staggered, one after the other.
But like I said earlier, I was just a kid at the time I heard this and could be wrong.
Also, when I was at Bentwaters/Woodbridge there were three squadrons of F-101s and a squadron of F-100s. The F-100s were at Woodbridge.
Join Date: Apr 2005
Location: Temporarily missing from the Joe Louis Arena
Posts: 2,131
Received 27 Likes
on
16 Posts
"If I'm awake, everybody is awake."
Dawn chorus a'la VC10.
Dawn chorus a'la VC10.
Part of the mechanics of the 101 pitch-up was due to what happened to the flow over the wing as the AoA became excessive. The wing tips were the first place where the wing would stall and this moved progressively inboard. Due to the wing sweep this had the effect of moving the centre of lift forward on the aircraft, IE the remaining lift was now too far forward on the aircraft.
When the flow over the horizontal stab became disrupted there was no longer enough control to prevent the aircraft pitching up. You could pitch up at any speed if you were hard enough on the AoA, as one of our pilots discovered doing an airtest. He pitched up at about 400 KIAS and the aircraft was out of service for about six weeks due largely to over stress of parts of the airframe.
He said he was a passenger for the first few seconds and it was a very rough experience.
This was early sixties when they were fairly new to the RCAF.
When the flow over the horizontal stab became disrupted there was no longer enough control to prevent the aircraft pitching up. You could pitch up at any speed if you were hard enough on the AoA, as one of our pilots discovered doing an airtest. He pitched up at about 400 KIAS and the aircraft was out of service for about six weeks due largely to over stress of parts of the airframe.
He said he was a passenger for the first few seconds and it was a very rough experience.
This was early sixties when they were fairly new to the RCAF.
I can remember a shot taken at Edwards where a 100 or 101 suffered from pitchup on late finals. The pilot tried to power out of it but all it did was an afterburner hover taxi and then came to a sorry end in a hangar complex.