View Full Version : F-101 Question
Jane-DoH
28th Jun 2011, 20:04
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
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.
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?
Rossian
28th Jun 2011, 20:12
....is "clunkdriver". There can't be too many others who've flown it, around these hallowed halls.
The Ancient Mariner
BEagle
28th Jun 2011, 20:37
Err, no.
CF-100 = 'Clunk'
CF-101 = 'Voodoo'
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).
Pontius Navigator
28th Jun 2011, 21:49
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?
con-pilot
28th Jun 2011, 21:59
The only problem on take-off was getting the nose gear up quickly enough after rotation as it would hang at around 290 KIAS.
I can remember as a kid watching F-101s taking off and it seemed like at least one out of every five or six would still have the nose gear still down after the mains were up. My father said that usually it was the newest pilots in the squadron that were the guilty parties.
But not always. :E
It is possible he may have been on the CF101 rather than the CF104. Is there a similar list for aircrew fatalities?
I do not know of a list, but I have never heard of that accident, and I am sure I would have.
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 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.Obviously, the Cdn test pilot did not read the Voodoo handling notes before flight, which to me does not seem very professional and caused unnecessary damage to the aircraft.
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 !
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 !
Flash2001
29th Jun 2011, 13:36
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!
Old Photo.Fanatic
29th Jun 2011, 14:08
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
"If I can't sleep, nobody's gonna"
I had not heard that one before, but very appropriate ...
con-pilot
29th Jun 2011, 17:07
I remember in 1959 or 1960 going to the USAF Bentwaters airshow in RAF Uniform
That was when I was there. I'm glad you enjoyed the airshow, my father was in charge of most of them. He'd be very happy that people still remember them.
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.
Fareastdriver
29th Jun 2011, 18:11
"If I can't sleep, nobody's gonna"
The Royal Air Force's translation of that is:
"If I'm awake, everybody's awake."
The Helpful Stacker
29th Jun 2011, 20:05
"If I'm awake, everybody is awake."
Dawn chorus a'la VC10.
innuendo
30th Jun 2011, 06:14
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.
Fareastdriver
30th Jun 2011, 06:40
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 hanger complex.
Jane-DoH
30th Jun 2011, 07:17
Fareastdriver
That was an F-100C IIRC
Argonautical
30th Jun 2011, 09:49
Then there is the question of how does a Voodoo pilot take evasive action?
Answer - He undoes his straps and runs around the cockpit!
Actually, the Voodoo cockpit was almost big enough to do that :O
On one long cross-country (in a four-ship) coming back from the US, my backseater got bored and after a bit of maneuvering, he unstrapped, undressed, and at his prompt I took over the lead while he gave the rest of the section a "full moon/pressed ham" at Angels 35 !
DALMD-11
2nd Jul 2011, 04:19
There can't be too many others who've flown it, around these hallowed halls.
Well, there's at least one ex-Voodoo driver here. I flew the RF-101G/H and the RF-101C from 1967 to 1973 in the ANG. This included the Active Duty recall in 1968 with a TransPac deployment to Japan. With lots of airspeed and low altitude, the 101 could be "horsed around" quite a bit. A hard turn would produce buffet before the Pitch Up horn would sound. Most of my time (800 hours) was in the G/H model. My unit didn't get the C model until around 1971. It was always my personal impression that the C was more sensitive to the Pitch Up horn than the G/H. The hung nose gear stories are true.
innuendo
2nd Jul 2011, 05:54
CF-101B from '62-'64. Not the most forgiving aircraft in the world to fly but it had the means to do what it was meant to do. :ok:
http://jetset.zenfolio.com/img/v4/p54914156-4.jpg
http://jetset.zenfolio.com/img/v23/p57639928-4.jpg
http://jetset.zenfolio.com/img/v22/p585441069-4.jpg
Apologies for the quality of the last photo but it is a scan of a print on Pearl paper which does not scan well.
CF-101B from '62-'64. Not the most forgiving aircraft in the world to fly but it had the means to do what it was meant to do. Oh Yeah...... AIR-2 Genie (http://en.wikipedia.org/wiki/AIR-2_Genie) :E:E
http://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/CF-101B_firing_Genie_1982.jpeg/800px-CF-101B_firing_Genie_1982.jpeg
innuendo
2nd Jul 2011, 07:38
From your Wiki link:
To ensure simplicity and reliability, the weapon would be unguided, the large blast radius making precise accuracy unnecessary.
That made your first priority after seeing the fire signal on your steering scope, getting out of the way of the "Large blast radius" so you did not become involved in it. Mind you if it ever came to that the world was in a pretty serious situation.:(
BEagle
2nd Jul 2011, 09:12
Many years ago we participated in a spot of affiliation with the 416 Sqn CF-101 guys at CFB Chatham.
The idea being that we were to attack their aerodrome and they would attempt to intercept us.
Running in a 300ft and having heard nothing on the RWR, we decided to climb to give them a sporting chance. Soon afterwards a CF-101 did its simulated 'vapourise a cubic mile of sky and anything in it' thing with a simulated Genie shot, then closed for an attempted Falcon shot.
Mistake. It didn't take long to fly a few wingovers, get inside his turning circle and trap him firmly in the windscreen. As he roared around at VC, we just sat in the middle of the turn at about 60° AoB.....
Listening to the playback tape afterwards was hilarious:
Pilot: "Where'd he go?"
Navigator: "Hell, he's in our six. How the f*** did you let something that big get behind us?"
Sporting serious headaches the next morning after the generosity of our hosts, 2 of us were offered back seat trips in the '101. 'Animal' went off in one, but the one I was due to fly in went U/S. Once the rest of the crew turned up, we cranked up the tin triangle and cruised gently back to Goose Bay.
Fun times!
DelaneyT
2nd Jul 2011, 13:17
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. --TLB
F-101 liftoff at 230 KIAS {?}
Sounds a bit fast for routine takeoff roll.
Were the tires rated for that high a speed ?
innuendo
2nd Jul 2011, 14:19
That 230 KIAS must be a typo. 175 -180 ish was more like it. A bit faster if you had external fuel tanks on. Landing was still pretty speedy, based on 3000 Lbs of fuel remaining and full primary armament, final approach was 175 KIAS with touchdown speed at 160 KIAS. For every extra 1500 Lbs fuel add 5 KIAS. In the event of single engine 15 KIAS on top of that.
The top figure in the check list is for 12,000 fuel, 205 final and 190 touchdown.
Landing with that much fuel would not be the norm and would probably involve hot brakes with that much energy to dissipate.
Still have my original check list.
Flash2001
2nd Jul 2011, 16:12
The Voodoo tyres were something. I think they were only good for 9 or 10 landings at best and only 1 if the landing was at maximum weight. In introductory training we were told that 1 main wheel contained enough energy stored in compressed air and stretched nylon to put a golf ball in geosynchronous orbit.
After an excellent landing etc...
That 230 KIAS must be a typo
Yes, that was incorrect. Things happened pretty quickly - not much time between rotation to lift-off.
Jane-DoH
15th Jul 2011, 03:55
BEagle
Mistake. It didn't take long to fly a few wingovers, get inside his turning circle and trap him firmly in the windscreen. As he roared around at VC, we just sat in the middle of the turn at about 60° AoB.....
You were an Avro Vulcan pilot, I would assume? Despite being a bomber, it was pretty maneuverable from what I remember reading about it (I don't know how many G's it can pull at max) especially with those huge, thick, large-span wings.
Listening to the playback tape afterwards was hilarious:
Pilot: "Where'd he go?"
Navigator: "Hell, he's in our six. How the f*** did you let something that big get behind us?"
I'm surprised the F-101B pilots didn't realize that the Vulcan's had a turning advantage over them and didn't just use the vertical more liberally.
Delaney
F-101 liftoff at 230 KIAS
I didn't find it unusual considering the small wings the plane had. Regardless, a fully loaded F-105 would leave the ground at around 235 knots.
innuendo
That 230 KIAS must be a typo. 175 -180 ish was more like it. A bit faster if you had external fuel tanks on.
So you'd begin the rotation at 155 kts; then by around 175 to 180 you'd leave the ground?
The critical alpha for this aircraft must have been fairly low to have a takeoff speed like this and still be fairly close to stalling it when near takeoff speeds with full tanks...
everybody
If it's not classified, how did this airplane's turning performance (subsonic and supersonic), to planes like the F-104, F-105, F-4 and so forth?
Argonautical
15th Jul 2011, 08:32
"Voodoo Warriors" by Group Captain Nigel Walpole is a good book about the Voodoo.
If it's not classified, how did this airplane's turning performance (subsonic and supersonic), to planes like the F-104, F-105, F-4 and so forth?
If memory serves, corner velocity was around 420 KIAS. P sub S numbers were very similar to the F-104.
Jane-DoH
20th Jul 2011, 02:57
TLB
If memory serves, corner velocity was around 420 KIAS. P sub S numbers were very similar to the F-104.
Specific power were similar to the F-104 at subsonic speed, or subsonic and supersonic speeds?
clunckdriver
20th Jul 2011, 10:31
"Oh look! a Voodoo banking as if to turn! "This gem was broadcast inadvertantly at an airshow over the PA at one of our Eastern bases, as luck would have it the airplane noise resulted in a very small portion of the crowd hearing it, for which a certain junior officer was most relieved!
Jane-DoH
21st Jul 2011, 03:41
What thought processes motivated McDonnell in the creation of this aircraft?
As I understand it, it was supposed to be a fighter with supersonic capability that could fly long enough to escort a B-47 While it had the range, and speed; it's wings were too small to give it significant sustained maneuverability...
It seems as if they obsessed entirely on speed and range and focused on agility last...
What thought processes motivated McDonnell in the creation of this aircraft?
The same thing that motivated the US and Canadian Air Forces to purchase 807 of them. During the 1950s when the Voodoo was developed there was a growing belief that air-to-air missiles would negate the need for turning dog fights. Many designs therefore concentrated on climb and speed performance at the expense of turning capability.
McDonnell F-101 Voodoo*Interceptor / Reconnaissance Aircraft - History, Specs and Pictures - Military Aircraft (http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=73)
jamesdevice
21st Jul 2011, 17:04
weren't they specifically purchased to fire NUCLEAR air-to-air missile at incoming bombers coming in over Alaska / Canada? In other words, close-in capability was irrelevant: they used a stand off missile, they just needed to get in fast, fire , turn and get out fast to avoid the flash
I know they were originally conceived as bomber escorts, but - I understand - the role was redefined before the bulk purchases were made
Please see the posted link!
McDonnell F-101 Voodoo*Interceptor / Reconnaissance Aircraft - History, Specs and Pictures - Military Aircraft (http://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=73)
Jane-DoH
22nd Jul 2011, 03:58
Bevo
During the 1950s when the Voodoo was developed there was a growing belief that air-to-air missiles would negate the need for turning dog fights. Many designs therefore concentrated on climb and speed performance at the expense of turning capability.
You're sure you're not thinking of the Phantom?
The Voodoo as far as I understand in its original, non-interceptor version (F-101B), was equipped with 3 x 20 millimeter guns, 3 x Falcons, and 2.75 inch unguided rockets. As far as I know, the last two items were removed by the time the plane first flew, though TAC developed it as a fighter bomber; ADC developed the F-101B as an interceptor and fitted the provisions to carry either 4 x Falcons in a rotating pallet or 2 x Falcons and 2 x Genies.
jamesdevice
weren't they specifically purchased to fire NUCLEAR air-to-air missile at incoming bombers coming in over Alaska / Canada? In other words, close-in capability was irrelevant: they used a stand off missile, they just needed to get in fast, fire , turn and get out fast to avoid the flash
That was the F-101B, which was a variant of the F-101. It was designed to fill in the gaps until the F-102's reached operational strength. It ended up more or less replacing the F-89's in practice. It could carry nuclear (2 x MB-1/AIR-2 Genie) unguided rockets, or non-nuclear guided missiles (4 x AIM-4 Falcons, or 2 x AIM-4 falcons when 2 Genies were carried) in a rotating pallet.
I know they were originally conceived as bomber escorts, but - I understand - the role was redefined before the bulk purchases were made
As I understand it the plane was already flying by the time SAC decided it didn't want them. They wanted more range than they asked for earlier, and then decided that the B-52's range made them unnecessary (I disagree obviously: History has shown that bombers have much better survivability when escorted by fighters, and F-101 had a mid-air refuelling capability from the get-go, it even had refuelling receptacles which could use the flying boom, or the hose and drogue; the plane could have been refuelled repeatedly to keep it flying with the B-52's from takeoff to the penetration point -- at that point they would fly with it both in and out, then refuel on the egress). TAC, however took an interest in the aircraft as a fighter-bomber, and eventually ADC took interest in it as a place-filler for the F-102's.