This was one of the Flight Safety short films was it not? IIRC, this one was called "Flight Safety? Nothing to do with me!". Ended with Richard O'Sullivan lining up without clearance with someone on short finals.

The other one "Distractions" is probably better known. About a Jag Flt Cdr who forgot the MASS and lost an engine on take-off - couldn't jettison the tanks, and ejected too late.

Thank you, Gentlemen, very kind and illuminating. I did wonder about the "air cushion" concept such as helicopters have going for them but figured it probably didn't apply.


One more, for now, if I may?


During lift off in a conventional (or short) forward take off, does the aircraft rotate around the rear axle and gear? Just looking at it, the main gear leg appears to be aft of where as a layman I'd picture the CofG to be.

Embarrassingly enough having flown a fair few of each I can't answer the question. However it might help inform the debate to explain that a conventional and short take off are fundamentally different.

In a conventional you slam with zero nozzle and then apply progressive back stick at about 120 kts. Eventually some aviation happens. In a short take off you slam with zero nozzle (or ten if you want to keep the efflux off the tail) and then at a pre determined speed (or when the wheels skip) you snatch in a pre determined amount of nozzle - weight dependent but about 50 - and maintain the attitude with a little forward stick if anything.

I hate to be the pedant Orca, and as you know I'm not of the CFS persuasion, but I think we slammed with 10 nozzle on a CTO as well for the reasons you state...not that it matters, just nice to be talking about VSTOL again!!!

Not sure about other opinions on the matter but, with an armoury of quite a few different short take off options available, a CTO always felt 'wrong!' (or maybe I wasn't doing it right?! Conventional landings even more so; downright perverted, especially with a crosswind!

Helmut,

In truth all aircraft with tricycle undercarriage rotate around the main wheels during conventional take off. It is the pivot point, if you think about it. Also, the main wheels need to be behind the CofG otherwise there is a risk that the aircraft will fall on its arse when it's on the ground. Some, like F-35, have their mainwheels even firther back to make space for weapons spaces, etc.

Gents,

JF may well correct me, but I believe that the key aspect of a Harrier CTO is that it had a bicycle undercarriage layout, with the aircraft weight spread nearly 50/50 between the main and nose legs. In truth, the 'nose' leg was really a 'front main'. What that meant was that the Harrier couldn't really rotate about the aft main leg. Bicycle gear was very popular on jets in the 40s and 50s, see also B-47, B-52, Vautour. It was useful on the Harrier as it kept the main wheels away from the hot nozzle wash. (Again, so I've been told)

I have also been told that the undercarriage was modified during development to give the wing a higher incidence to make CTOs (and conventional landings) slightly easier and to shorten the TO run.

Main wheel location (on normal tricycle layouts) is driven by lots of things, including ground stability as well as takeoff and landing loads and dynamics. For naval aircraft, there also have to be margins for aircraft moving backwards on a rolling deck, as well as the peculiarities of cat and trap ops.

On F-35, the main legs are actually located outboard of the weapons bays, their fore and aft location was mainly driven by structural aspects. However, during the weight saving effort, the main legs were raked forward to reduce the control loads required for CTOL (and STOVL) variant rotation during takeoff.

It should also be noted that the F-35B nose leg takes only about 10% of the static load, compared with the 50% of the Harrier. Many of us on the programme were surprised at the 'spindly' look of the nose gear, but that was just a result of our own ignorance. It's actually a tough little mother.

Hope this helps, interesting thread (until this post, that is)

Best Regards as ever

Engines

Forgive a silly question but did the engine / fan produce much of a gyroscopic effect on what is arguably a short aircraft when the throttle was slammed?

The HP and LP spools rotated in opposite directions to minimise gyroscopic effects.

Helmut

The Harrier as Engines said has a bicycle gear so cannot rotate during any sort of ground roll (think B-52, B-47 etc) because with a bicycle CG is so far in front of the rear leg.

For this reason the wing is mounted leading edge up on the fuselage to that it has 8 AoA during any ground roll thuis generating significant lift with a few knots. (I was not aware that this changed from the P1127 prototype days Engines - but my awareness has always been a bit variable)

This inability to shed wing lift when doing a conventional landing is the reason for some of the fun seen after high speed landings on old conversion movies in the days before two seaters or simulators. It is also the reason the outriggers did not break off when going sideways on some of them.

John,

Thanks for coming back.

I was told that the tweaks to ground attitude were very early on in the P.1127 programme, possibly even prior to first flight.

I was also told that the whole issue of landing gear was a problem area for the programme from day one right up to (and after) the GR.1 entered service. Shimmy on outriggers, bounce on landing, problems with nose steering - the team at Dunsfold just about had the lot. And they had to cope with rough field ops. The end result was tough, dependable and above all in a powered lift aircraft, light.

Undercarriage design and development is another bit of aircraft engineering that looks easy until you try to do it. Again, us Brits have a very strong track record in this area. So do the Russians - some of their designs are novel, and highly effective.

Best Regards as ever to all those trying to get the wheels to go up and down and stay on and go around,

Engines

Engines

Yes the u/c was a problem for 8 years from the first tethered hovers to a year or so before entry into the RAF in '69. It was completely solved by Ralph Hooper's idea of a self shortening main leg.

With a bicycle the gear has to be designed so that the main gear takes the intial landing impact loads. This means the nose and outriggers are still clear at touchdown (or should be!). When the main starts to shorten the nose and O/R get in the act and the aircraft stays flat. However after the vertical descent has been killed only the weight remains so the main leg starts to extend again and in the case of the Harrier this puts the O/R back in the air so the thing flopped one side or the other giving very bad ground handling and (because of the aforementioned lift due to wing AoA) a tendency to shoot off the side of the runway especially with crosswinds.

The self shortening leg was brilliant. On touchdown the oil that did the job of absorbing the impact was then fed into an accumulator rather than kept at the top of the leg under pressure as with a normal oleo. Thus there was no rebound from the main leg and so the jet settled wings level. When the main leg next left the ground on a takeoff, its weight made it fall down and fully extend sucking the oil back into the oleo for normal operation on the next landing.

:{

So sorry to learn now that my immaculate VLs and VTOs were due to oil and some spurious accumulators, rather than my outstanding skill!!

Back to the potting shed and a bottle of red wine!! It all seems so much better there!!:)

I hear your accumulator banter engines old fruit - but you could still get the old girl to bounce if you weren't pretty quick with the throttle to idle when you landed/ hit / impacted!

I think the Harrier design was staggering given when it was done. Those were clever boys. I was most impressed by the fact that the hot and cold nozzles didn't produce an uncontrollable pitching moment. Probably quite straight forward to a grease chimp, but it impressed this stick monkey!

By the way MSOCS old friend, the conventional in the Harrier II was a doddle!;)

Bomber and orca

Good to hear from you if rather disappointing that I clearly did not explain things properly. My comments were purely about ground handling and how that was improved by the self-shortening leg which allowed both outriggers to be in contact with the ground after any landing was over.

The proclivity to bounce (or otherwise) on a VL is a whole new topic and of course is totally down to the pilot not the aircraft design. Descending at a steady rate for a VL the 8 tons of jet clearly has some momentum based on that rate of descent. However because it is a steady rate of descent the weight of the aircraft is totally supported by the donk. Thus if the throttle is not chopped on touchdown the gear only has to deal with the momentum and not the weight as well, so the springs on the nose and outriggers will easily push you back up to x ft and you have the whole thing to do again.

God I hate people who have to explain their jokes.

As Engines pointed out there were other problems with the gear especially the outriggers but these were all sorted by the end of the development period.

Never flown the Harrier (though did once have a go in the sim) - however, I hope I am not the only non-Harrier reader to be enthralled and educated by John Farley's posts. We have never met, but many thanks John.

There is always more interesting detail to follow (if you are so inclined) in most aspects of this sadly discarded aircraft.

I seem to remember that the tendency to bounce on VL required a fairly crude fuel bypass modification to the complicated fuel control system in order to achieve rapid wind-down on throttle closure.

The castoring outrigger wheels sometimes stuck at odd angles, leading to worse shimmy than that which they were supposed to stop. The wheels were fixed some time in the mid 70s.

The wide range of landing speed options required a wing that stalled gracefully, rather than suddenly losing lift. The Harrier 1 wing had a fascinating range of devices on it, including the oddly-labelled vortex generators added in 2 steps. Harrier 2 had a much different wing, which may have shared the odd quirk with the F18 wing due to a stray algorithm in the MD computers.

Only by the UK for reasons best not gone into here.

The USMC have declared they will not start rundown until 2027.

The Indian, Thai, Spanish and Italian navies all seem happy with the jet with no end off service dates announced.

Well, as a student, I was such an expert in the art of the power bounce that I starred in the Harrier Horror Movie :). Do I win US$8.38?

(Very pleased with the II & II+ solution to steal power when the wheels hit the ground so one couldn't bounce up again so easily).

Watching Bloggs perform conventional landings whilst peering nervously to one side of his head from the back of the T4.....oh, deep joy :ok:

Does the need to absorb vertical impact momentum and mitigate bounce have anything to do with the tyre issues on the F-35B? It seems that there is a conflict between VL and CTO requirements but it is not clear what it is.

LowObservable

Dunno why the type of landing should affect the tyres - unless of course you are trying to keep below a wheel/tyre RPM limit at very high conventional touchdown speeds.

I believe the F-35B has been experiencing high wear rates on the tyres/tires. The B has a different tire maker than the A and C models. Perhaps a design or manufacturing issue. I wonder if heat from V/STOL operations and the rough non-skid on deck contributes to the high wear rates.

Good article here: http://defensetech.org/2013/09/19/5t...eration-tires/

JF, Guys,

During the F-35 weight reduction effort all three variants were looking for pounds to lose and the landing gear came under scrutiny. (yes, should have been done during design first time around but LM didn't have a Chief Designer at that time and they took their eyes off the weight ball).

Anyhow, it was found that some conservative assumptions had been made for landing speeds, weights, temperatures, surfaces, runway lengths, repeated landings etc., which had led to fairly chunky wheel and brake units. On further examination, the LM team found some new tyres (I think they were French) that offered good performance with significant weight reductions. I think that they ended up with three tyre types for A B and C, choices driven by conventional landing weights/usage spectra. Brake units were also tailored across the three variants (remember that the F-35A and C had serious weight issues as well).

So, the main balance for F-35B was to provide the best possible conventional landing braking performance (and tyre life) while keeping weight down as much as possible, driven by the need to achieve the mandated Vertical Lift Bring Back (VLBB) figure.

Hope this helps a little

Engines

Engines

Many thanks.

JF

Noprobs,

I think the crude device was termed the Pressure Drop Regulator...pushes spectacles up nose with right trigger finger...it was certainly PDR on all the diagrams.

Some great info here, thanks guys.


I was looking at a pic of the Harrier (II, I think) with the gear extended and I note the nose gear doors are closed at the tyre end of the system but the leg end is obviously open around the pivot end of the leg with a very tight opening allowed around the leg. Why is this? Does the door-closed system prevent damage to internal systems (eg Hydraulics) during the vertical take off or landing, from FOD produced by the downward thrust or is there something more to it?

Clarification on frs sea harrier behaviour
 

Dear john farley sir....

I am one of harrier frs mk 51 operators from india.... recently in one of the aircraft during AMTFi noticed a peculiar problem.... the details are as follows...

1. During trim checks... at 450 knots, with mid flaps.. the rudder and aileron trim is out by half gauge width... with nozzles aft and undearriage up... however... during 190 knots with flaps mid, nozzles aft, uc down the trim required is neutral...

we carried out rigging and took her up again.... now the defect reversed... ie at 450 neutral trim and at 190 knots trim reqd is high...

2. Another observation that, at any speed during straight and level flight, just by increasing engine speed and with no increase in speed the aircraft is rolling to left....and on decrease in engine rpm the aircraft is rolling to right....

we are trying to find a solution but unable to find any reasons.... could pls suggest some ideas as to why it should happen....we ecently changed the engine.... previously there was no defect.... regards

achillesat23

Poor you! Over the years there have been many cases of odd trim changes.

When you think about it there are so many things that can affect the trim of a Harrier aircraft that it is amazing that there are two aircraft the same!

However you say you carried out rigging checks but not if you changed anything or things. So I would suggest the following:

Make sure the aerodymamic control surfaces are rigged within limits including the flaps when in the mid position.

Carry out the 450 knot check carefully and adjust the gauges as necessary to indicate zero on both.

From now on only adjust/change one thing per flight

If you are still unhappy with the 190kt gear down, flaps mid and nozzles aft situation look at your engine options.

Individual nozzle angles when aft selected. (having a rear one down even a little can change a lot of flow at the back end)

If these angles need changing re fly and do the 450 check and adjust again.

If still unhappy:

Swop the front nozzles (L/R)

Reset the 450 kts as required.

Finally - and this is the most likely cause of the confusion - swop the rear nozzles. These of course contain the engine trimmers which have been known to significantly affect overall aircraft trim with changing RPM at constant IAS. We have also found moving a trimmer's position in its own nozzle can also help.

Reset the 450 kts as required because in the end of course what really matters is the 450 kt trim setting as this affects gun aiming accuracy.

Good luck!

JF

Helmut, have you recently acquired a Harrier, without an owners manual?

Final Phase of FRS MK51 IN issues..
 

Dear John sir..

In first place I would like to convey my apology for not getting back on the harried unintended roll issues as I had got transferred out shortly there after...

A brief on the previous problem.. We had carried out all kinds of combinations as you suggested and with no result we were about to name "the rogue" as the rogue again... However the problem was solved by replacement of fin.. Which to our surprise the least suspected part... The aircraft is still up in the air and she is as beautiful... Just did a 90deg turn during hover and landed her...

Thank you sir...

Thank goodness. I've been worrying about that for a year and a half now.

Harrier hover performance and its implications..
 

Dear john sir...

We are presently at the final phase of Harrier operations and are faced with new problems.. Till date the Harrier never ceases to amaze me with respect to its capability and technical brilliance this aircraft posses...

Coming to the issue at hand...

Presently the engines that are being rolled out of the overhaul facility are sitting close to high margins due to use of various components including turbine... Notwithstanding they are within test bed acceptable limits...

However, when installed on aircraft... The hover performance values are sitting extremely high at Wh -7(minus 7) and Jpt of +40.... Which is completely out of the graph itself... We are faced with the dilemma...

The fact that I am again back as Sqn Harrier Eng Officer forces me to look to various factors and forces me to think out of the box ideas to sustain the jets for some more time...

My concerns and questions are as follows:

1. What does the hover performance indicate with regard to overall health of the engine... (The case in point is.. Though the perf hover values are high.. The ELR counts are less.. It eats abt 3 to 5 per normal sortie.. That's in Indian conditions )

2. Can the aircraft/ engine still be exploited with such hover values primarily for non VSTOL flight regimes keeping VLanding to completley minimal (beggers can't be choosers.. So is the question )

3. We had 3 engine surges during PRL checks in last one year... Is it anyway connected to poor hover performance leading to poor perfoance of the engine through out normal flight envelop...

These things have not been answered in publications and manuals.. It becomes imperative to draw conclusions... The primary aim being not to reject an engine without proper reason... The case in point being... VSTOl opeartions are not that imp as we are trying to sustain this beauty just for few more months...

Your valuable inputs will be greatly appreciated sir... Hope I haven't made a fool of myself asking this... On the lighter side sir...

Regards... Probably Last Engineer of Legacy Jumpjets... Achilles...

Harrier roll
 

Ha-ha.. Thanx a lot for concern and extremely sorry for late reply.... Loved to see you remembering abt the problem....

Going through an old photo album recently I found this unusual shot of a Sea Harrier on RFA Olwen, I'm guessing its John F ? Love to hear any good tales of trials flying off a flight deck that small !

Nice to see that the bona jet is still out there and you are still having the old fun n games trying to keep it in the air

The Indian Navy retired the Sea Harrier during May 2016. Replaced by the MiG-29K.

Indian Navy bids farewell to iconic Sea Harrier, welcomes MIG-29K fighter jets | Latest News & Updates at Daily News & Analysis

peterperfect
 

Not me sir. Size is not a problem as given the approriate visual cues you can easily position a Harrier VL to a couple of feet.

However - and it is a big however - ship motion is what it is all about. That can change everything.

Deck landing facing aft with the wind from astern was good for a laugh.

What a great thread

JF - bought a copy of your book at the LAA Rally - a brilliant read, and brain cell provoking. Now reading it for the second time. Many thanks, I hope other readers enjoy it as much as I am