Lifting Nosewheel on T/O - Why So?
 

It seems that lifting the nosewheel off the bitumen at a certain speed was de rigueur on early British jets, certainly the Comet and Vampire. In the Comet case the procedure was responsible for the first two crashes, and brought about the introduction of the Vr call concept. The question is, what was the thinking behind the lifting of the nosewheel? Particularly in the case of the Comet, if there are any drivers from that era reading. Was it the same on the Canberra and V-Bombers?

Thanks in advance to all.

I may have missed something, but if you don’t lift the nosewheel you’ll end up in a ditch at the end of the runway.

I think the procedure was to lift the nosewheel and then let it down again wait for some time before taking off for good.

Not only early jets. Watch the take off from 2 minutes in (and the float on landing at the start!!).

From the Meteor F 8 Pilot's Notes:"Ease the nosewheel off the ground at approximately 90 knots; the aircraft will unstick at 110 - 120 knots with 1/2 flap down" - i.e. present the wings to the airflow at the appropriate angle of attack and the aircraft will fly off when it is ready. Of note a couple of paragraphs later it states: "The safety speed is 150 knots (155 knots on aircraft with large intakes)". This speed is usually known as V2 therefore between 120 and 150 you would not be able to control the yaw following an engine failure and would have to throttle the live engine back and land ahead!!

On the Vampire you lifted the nosewheel to prevent Nose Wheel Shimmy which was pretty fierce. On the T11 if you got shimmy the instruments became unreadable. On the Vulcan B2 with the 301 engines we called Rotate but it was going to go up whether you liked it or not (unless you pushed the control column forward).

ACW

Minimum take off roll.

Keeping the nose wheel on the ground reduces induced drag so the aircraft accelerates faster and reaches take off speed sooner with less runway, tyre wear, engine life, etc.
Rotating at about 15 knots before calculated take off speed enables the pilot to pull off the aircraft smoothly without snatching and risk scraping the tail.

At least that is what I was told at my Valiant conversion course in 1962.

Hmmm, that technique is likely to causes a tail scrape on most modern passenger jets and even if it doesn't, the extra drag will significantly increase takeoff roll.

As demonstrated all those years ago, not a great idea on big jets because of drag rise.
I'd guess, less of a problem on props because the propwash directs the airflow along the chordline of the wing.

Re rate of rotation, never ceased to surprise me how many captains, who should have known better, rotated too fast. It wasn't due to lack of training or comment by trainers.

ORAC, I'm guessing yer man in the B727 was:
a) Trying too hard for a smooth touchdown. (Hate it when that happens)
b) Avoiding nosewheel banging along on a less than smooth surface. (I usually just put one wheel each side of the lights :rolleyes: )
Time he politely told the boss some facts about big jet handling. Although, TBH, at their TO mass they can probably get away with it.

Early mark Canberra PNs didn't call it Vr but originally said that the nose should be raised 5kt before the calculated unstick speed, and they did warn that allowing the nose to rise earlier would extend the T/O run. Eventually it dawned on someone that the gap between unstick and Vmca could be reduced a bit by keeping the nosewheel on the runway for longer. Unfortunately tyre limitations meant that the nosewheel had to be raised at not more than 140kt, which was still way below Vmca.

Royal Air Marco takeoff.......

As an aside, why are the relevant speeds called out as V1 and V2 on some types, and as "decision" and "rotate" on others? The latter terms were always used on the Victor, whereas I recall V1 and V2 being used when I flew as "supernumerary crew" on various RAF transport types.

No you didn't, I did. In the case of the Comet the nose was lifted off at 80 knots, long before the unstick. The first two Comet crashes were caused by the procedure, one getting airborne in a stalled state, the other ran off the end on take off because the induced drag imposed didn't permit acceleration within the runway confines. Too high an attitude of course, but the difficulty was in judging same. Just interested in the "why" of the procedure.

Thanks for the Vampire shimmy explanation.

Lifting Nosewheel on T/O - Why So?
 

Could the ONLY reason for lifting the nose wheel on T/O possibly be the avoidance of water/slush ingestion into engine intakes, particularly rear mounted engines ? This was a technique used by SAS DC9s in the past to prevent such an occurrence.
The strategy was limited to raising the nose wheel only about six inches from a contaminated runway until Vr was called from whence the T/O was SOP. And it worked very well on the shorter -10s and -20s.
You will of course be aware that the later DC9-30s and MD80s marks were fitted with a nosewheel deflector plate to reduce the directing of any runway contamination into the engines.

I also accept all your arguments regarding degraded performance, possible tail strikes and possible loss of directional control in the event of an engine failure ! :ok:

The film Cone of Silence gives a good insight into the hazards facing early jet airliner operation. The 'Phoenix' (Avro Olympus-Ashton) aircraft flown in the film suffer a number of accidents due to the nosewheel being raised too early - exactly as happened in some early Comet accidents.

My Vampires used to shimmy on landing.

You always learn something new everyday!!

On the Dominie the nosewheel tyres were 'chined' so as to throw any standing water/spray sideways and away from the rear mounted intakes.

You might be interested in what D P Davies had to say about the Comet 1. Start at around 46mins - but the rest is rather good too!

You can listen to all his interviews here, they are ALL well worth listening to:-
https://www.pprune.org/tech-log/6029...-aircraft.html

V1 and V2 are not quite the same as decision and rotate. I guess V1 does equate to decision speed, ie you're no longer going to be able to stop. V2 is the nominated speed to fly once airborne but still with any take-off flap in the event of an engine failure. It's effectively your best climb-angle speed and used until you reach your acceleration altitude.

I guess raising the noisewheel was used on types which were flown off the runway as opposed to being rotated more aggressively and 'hauled' off. Ie, once the nosewheel is up the aircraft will then fly itself off the runway when ready.

Not in the same class I know, but for takeoff in the Shadow microlight, you commence with the sidestick pulled right back until the nosewheel lifts, then ease forward to maintain a positive angle of attack(and avoid the tail bumper striking) . The aircraft flies itself off when ready at about 70 kt.

I seem to remember the F4 nose came up at about 150 kts and I lifted off at about 185. I know the wheels had to be in by 250.

Converted onto Meteor VII (T) in early '50. Told to "raise nosewheel off slightly at 85 kts" (to avoid nosewheel strut getting a battering), pull aircraft off at 125 kts (it did not "unstick" cleanly).

Danny, a 7 t from my albums.

V2 is the speed that you will reach (all engines operating) at the screen height of 50' (old types) or 35' (newer types). It is also the speed at which: " A sufficient margin of control exists for the average pilot with the a/c in the T/O configuration (ie flap) to maintain directional control whilst achieving the maximum climb angle following failure of the most critical engine."

Sleeve Wing , concur with avoiding water / slush /snow ingestion . We used same technique on all marks on Trident .
In those conditions ,
''V1'' called and is stop /go decision speed .
''Rotate'' called at rotate speed [ Vr ] .
''V2'' is engine out safety speed . In wet conditions , gives a screen height of 15 feet! Talk to BAC111 crew out of Basel on a wet day with and engine failing after V1 ...
With the modern twins , they are mostly way over powered in the 2 engine t/o case , and thus very often V1 = Vr .

rgds condor .

TTN #12

IIRC the Victor K1/1A used "Go Speed" and "Stop Speed", usually in the correct order or simultaneous at Marham. On Trails, in places like Masirah, it was not unusual to have to accept a 10 knot gap between "Stop Speed" and "Go Speed" to lift the required fuel load. Not Perf A !!

A couple of thoughts( not knowledge ) about lifting the nosewheel early. Was this a technique required by the early tricycle undercarrige on such as the Airacobra, and taught to us by the Americans? This was then carried over to the early jets as "that was the way to do it" with tricycle undercarriage.

Nosewheel tyre speed limits could also have been a problem. Certainly with the Canberra, but could also be limiting with the VC10 at high elevation places like Nairobi. IIRC the limit was 200 MPH!

...
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.... Coz we always done it that way !!!

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roving (#24),

Thanks - nice pic - the Typhoon of its day. Preferred the Vampire to fly, though. It was a bad time for Meteor training: the accident rate was appalling for a couple of years.

Danny42C - interesting Metoer thread https://www.pprune.org/military-avia...teor+accidents

You'd hardly fit 200 MPH tyres on the nose-wheels with 225 MPH ones on the mains! Yes, at Nairobi, with a typical OAT of +25C, the Type 1103 VC10 (standard, but with "super" wing) was limited to a TOW of 140T with 200 MPH tyres, which would reduce the RTOW by a tonne or so. By the early 1970s, all BCAL VC10s were fitted with 225 MPH tyres for that reason, as we were operating NBO/LGW direct.

Sleeve Wing,
Instead of your DC-9's water deflector on the nose gear, the VC10 and BAC 1-11 nose-wheel tyres had integral chines to deflect water downwards. That reduced water ingestion into the engines, but obviously did not protect them from burst-tyre debris...

H Peacock,
Love your description of aggressive rotation and aircraft being "hauled off" the runways nowadays! In fact, a steady rotation rate of about 3 degrees per second is typical, to avoid tail-scrape on long-body types.

Surely the nose is lifted to increase the angle of attack, and thus get the thing to fly in the first place?

Chris Scott

As far as I remember the RAF VC10s were limited by Nosewheel speeds rather than Mainwheel speeds. I will not argue about the actual figures as I have not made an ODM calculation for 20 years and do not have one to hand.

Perhaps BEagle can throw some light on this.

VC10 tyres
 

TT

Your grey matter is clearly well preserved by the vin rouge-have just checked, RAF VC10s were fitted with 200 mph ie 174 max gs nosewheel tyres.

In which case, for anyone else who may be interested :O , the T/O performance would have had to be predicated on a 200 mph (174 kt) max ground-speed, even if the main-wheel tyres had the 225 mph rating. The operation I was referring to was in the early 1970s, but maybe by the 1990s or later the manufacturer was no longer offering the special nose-wheel tyres with "chines" for the VC10 with the 225 mph rating. (The main-wheel tyres did not have chines.)

And, returning to topic, lifting the nose-wheels off the runway prior to VR increases aerodynamic drag and is therefore not an option to improve performance.

You RAF guys ended up operating almost every original type of VC10 (albeit modified in most cases) except the one that I did. You must have had many different sets of graphs or tables - or was it all computerised? ;)

Maybe some brilliant person reckoned that if a tail-dragger had to lift the tail on takeoff roll, then a nose-wheeler had to lift the nose?

Going through some WWII flight manuals seems to be something in what you say. The British B-24 notes say lift the nosewheel when elevators become effective to prevent nosewheel pounding, whereas the US notes say the reason for lifting is that the aircraft sits with a negative angle of attack.

B-29 says to relieve pressure on the nosewheel at 90 mph to lengthen the oleo. Nosewheel should not be more than one inch off the runway at any point in the roll and aircraft will fly itself off.

Notes on the P-38 mention a negative angle of attack and at 80 mph pull back steadily and firmly for lift off at 100 mph.

Vascodegama.

Thanks for the endorsement that I have not (yet) lost all my faculties. However, down here it is normally chilled Rose rather than Vin rouge, due to the sun and high temperatures. At the moment I am sipping chilled Guinness. I have just returned from a trip to Spain with a couple of cases. Unfortunately I was not able to organise a tanker!

Chris Scott

The RAF had the VC10CMk1, which was the new aircraft for 10 Sqn. These were a Hybrid with Standard (ie short) body and Super wings. These had the ODMs for the type. When we acquired the Tanker aircraft we had old BOAC/Gulf Air Standards as K2s and Old East African Airways Supers as K3s. All the aircraft had the same standardised engines.

The Tanker ODMs were produced to different standards to the original RAF VC10 C1s, and did not cover the same operating limits (more limiting) as it was not envisaged that we would operate worldwide, thereby saving a couple of quid in their production.

The ODM was produced for the K2(Standard) with fiddle factors to be applied to the K3. The K4(Ex BA Supers) had the same performance as the K3s.

We had Regulated TakeOff Graphs(RTOGs) produced, for the various types,
at selected airfields as well as Balanced Field Graphs you could use if Max TOW was not a problem.

If you had to operate at MTOW from an airfield that was not in the book of RTOGS it was back to struggling with the ODM.