VTOL question

[Sue Vêtements]

This is probably a bit silly and obvious why it never got developed, but a comment from uxb99 on the Ukraine thread got me thinking

While the Harrier could take off vertically it is my understanding that it could not do so with a meaningful combat load

Was that because of the extraordinary amount of fuel it probably needed to rise vertically, or just the penalty of lifting excessive weight during that phase, or more likely bot? But here's my question: Was there ever any investigation into a method of providing fuel via a ground connection until it was ready for the transition to level flight?

It'd be a bit like AAR in a way and would overcome much of the initial fuel use during the VTOL phase of the flight. I can see many reasons why you wouldn't want to do this, but was it ever even considered?

[Jhieminga]

It's a simple thrust v weight issue. The thrust of the engine is limited, so if you want to lift more, you need to add a bit of aerodynamic lift to the equation, or in other words: forward speed so that the wing starts working. You wouldn't be able to wind out the fuelling hose at that rate.

[NutLoose]

Ship wise they looked at the skyhook, the concept was to reduce the required size of the ship operating them and also allow them to bin items not needed such as the under carriage thus allowing more fuel / armaments,

read

Skyhook (http://www.cmlx.co.uk/hawkerassociation/hanewsletters/hanewsletter041nvu/skyhook.html)

https://www.secretprojects.co.uk/threads/skyhook-harrier-carrier.2372/

[Mogwi]

Skyhook was a mammoth brain-fart from a team who should have known better. It would have been the grandson of the CAM ships of WW2; short range intercept with a cold bath for a debrief. Mad!

Mog

[tartare]

Mog - was the reality that it would have been too difficult to return and dock with the Skyhook due to pitching/rolling of the ship?
Out of interest, why was it thought of as a crazy idea?

[POBJOY]

Rather like the rubber deck, where you 'flopped on' (sans u/c) still using the arrestor gear.!!!!

[chevvron]

The concrete base built for the rubber landing deck is still in situ at Farnborough.
I was told years ago by one of the early 'radio operators' at Farnborough that it took many tries for Winkle to get it just right before he actually put it down. By this time it was realised that all this effort landing the Vampire would come to nothing because the boffins had yet to devise a method of getting it off the rubber deck to tow it clear.

[longer ron]

Skyhook was a mammoth brain-fart from a team who should have known better. It would have been the grandson of the CAM ships of WW2; short range intercept with a cold bath for a debrief. Mad!

Mog

Absolutely agree Mog - I worked at Dunsfold for 16 years and it was the most bizarre Trial I ever saw there :)

[pasta]

For a deep, if slightly techie, dive into the design of the Harrier, and in particular the Pegasus engine that it was built around, look no further than this excellent book: https://www.amazon.co.uk/Pegasus-Heart-Harrier-Development-Operational-ebook/dp/B00KTM7IRW/ref=sr_1_1

Edit: Looks like it may be out of print, but the Kindle edition is available.

[ORAC]

There are other options if you want to get airborne carrying more fuel without a runway….

https://youtu.be/75qnxMd1YSY

[mikeoneflying]

The zero length launch -- USAF did quite a lot of work on this in 1950's.

Was thought to be a way of dispersing aircraft away from airfields.

For example fire the aircraft out of a barn on a farm!

[Mogwi]

Mog - was the reality that it would have been too difficult to return and dock with the Skyhook due to pitching/rolling of the ship?
Out of interest, why was it thought of as a crazy idea?

Yes, RTB to be speared by a Leading Hand in a rough sea was not a good option. In a lot of ways, it was a solution looking for a problem. To send small detachments of SHARs without undercarriage to operate from specially-built motherships up-threat of the main force just didn’t make any sense. There would have been no way to divert without damaging the aircraft and becoming a right operational PITA.

Atlantic Conveyor proved the concept of vertical-only ops from a small deck and that would have been enough for short-range intercepts. Intrepid and Fearless both acted as temporary homes for a SHAR during the hectic days post D-Day.

Mog

[Not_a_boffin]

Yes, RTB to be speared by a Leading Hand in a rough sea was not a good option. In a lot of ways, it was a solution looking for a problem.
Mog

This.

It almost had a second coming in the early noughties when someone at BAES tried to push the idea as a means of transferring large loads - container-sized - between ships at sea for RAS. It would have needed two systems, one on each ship (!!!!) and some intricate/comical means of handover.

Thankfully, common sense broke out fairly early on and it quietly disappeared. Hopefully never to be seen again, although someone will probably disinter it for "drones" in the next few years.

[hoodie]

... although someone will probably disinter it for "drones" in the next few years.
Already done.

There was an articulated gyro-stabilised UAV launch and recovery arm at Aero Friedrichshafen last year on the stand for WTD61 Manching.

[Video Mixdown]

Already done.
There was an articulated gyro-stabilised UAV launch and recovery arm at Aero Friedrichshafen last year on the stand for WTD61 Manching.
You make a good point. I don't really subscribe to this fashion for ridiculing ideas and inventions from the past that didn't work out. In some cases it was simply because the technology needed to make them work did not exist at the time, but may do now. Unless somebody is willing to try revolutionary ideas nothing new would ever emerge.

[NutLoose]

For a deep, if slightly techie, dive into the design of the Harrier, and in particular the Pegasus engine that it was built around, look no further than this excellent book: https://www.amazon.co.uk/Pegasus-Heart-Harrier-Development-Operational-ebook/dp/B00KTM7IRW/ref=sr_1_1

Edit: Looks like it may be out of print, but the Kindle edition is available.

And the Orpheous the Pegasus was built around ;)

[Davef68]

Atlantic Conveyor proved the concept of vertical-only ops from a small deck and that would have been enough for short-range intercepts. Intrepid and Fearless both acted as temporary homes for a SHAR during the hectic days post D-Day.


Even then, the alert Sea Harrier on Conveyor operated without underwing tanks to minimise weight on take off, hopefully with a nearby Victor to top up from.

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/500x354/blog_51_dms_falklands_025_8888af37644dc7d38ef4028e2b4faed86a 4d56fe.jpg

[sandiego89]

Even then, the alert Sea Harrier on Conveyor operated without underwing tanks to minimise weight on take off, hopefully with a nearby Victor to top up from.

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/500x354/blog_51_dms_falklands_025_8888af37644dc7d38ef4028e2b4faed86a 4d56fe.jpg

Dave/Mog, any idea on how much fuel the alert SHAR had on deck on the CONVEYOR or the Amphibs? Perhaps a 25 minute sortie? less? more? (without air refueling of course).

[Mogwi]

Dave/Mog, any idea on how much fuel the alert SHAR had on deck on the CONVEYOR or the Amphibs? Perhaps a 25 minute sortie? less? more? (without air refueling of course).

Very dependant upon density altitude. I can’t remember the basic weight of a SHAR with tanks and winders but I guess it would be c14,000lbs. If that is correct, a standard day (+15/1013) would give you c3,300 of fuel for a wet VTO, according to my ancient whizz-wheel. This equates to 25-30 mins cruise at medium level, with a small recovery margin. On a harry-redders day, that would be more like 2,300.

Mog

[uxb99]

If the main reason for the Harrier was dispersal just make jets that can take off from grass?

[sandiego89]

Very dependant upon density altitude. I can’t remember the basic weight of a SHAR with tanks and winders but I guess it would be c14,000lbs. If that is correct, a standard day (+15/1013) would give you c3,300 of fuel for a wet VTO, according to my ancient whizz-wheel. This equates to 25-30 mins cruise at medium level, with a small recovery margin. On a harry-redders day, that would be more like 2,300.

Mog

Thank you for the reply Mog. I know your SHAR course before you headed south was abbreviated, but would a typical squadron Harrier or Sea Harrier pilot practice many VTO's in training or field exercises? It seemed more common for demonstrations (especially early in the program with the parking lot and coal yard type events) and airshow type events, with STOVL much more common for operations. Non-event at the proper weight/desnsity?

[NutLoose]

If the main reason for the Harrier was dispersal just make jets that can take off from grass?

What you mean like this? :p

https://youtu.be/FFCfI4EaD0E

[Mogwi]

Thank you for the reply Mog. I know your SHAR course before you headed south was abbreviated, but would a typical squadron Harrier or Sea Harrier pilot practice many VTO's in training or field exercises? It seemed more common for demonstrations (especially early in the program with the parking lot and coal yard type events) and airshow type events, with STOVL much more common for operations. Non-event at the proper weight/desnsity?

Yes, all other things being equal, at the end of a sortie you would do some VSTOL for practice. Usually a VL, VTO or maybe a ramp launch to immediate hover and VL. Heavyweight VTOs were avoided unless operationally required because of the high number of engine counts incurred (JPT x time). All pilots were fully current in VTOs.

Mog

[twb3]

Spent some time on the AV-8B Mission Computer software team (as far as I know, a lot of my code is still running on the remaining USMC AV-8Bs). One of the functions in the MC allows the pilot to compute the shortest rolling takeoff distance for gross weight and conditions. The nozzle stop is set to the computed value and takeoff roll started with the nozzles full aft, then at the computed airspeed the nozzles are rotated to the stop and the aircraft lifts off.

[tartare]

Well there you go - was aged 15 at the time - and knew the Conveyor took jets down there - but didn't know they actually flew from the vessel as well.
Crikey.

[Mogwi]

It was possible to get a cleaner VTO by using 75 degrees of nozzle instead of the normal 82 (aircraft sat 8 degrees nose-up). This ensure that recirculating exhaust was vectored behind the intakes. Once clear of ground effect, 82 was reselected, if a hover was required. If not, accel away to wing borne flight was carried out as normal.

It was discovered that VTO performance was also better with gun pods fitted, as the exhaust bounced back off the ground and impinged on the fuselage between the pods. Hence the fitting of strakes if guns were not fitted.

Mog

[chevvron]

What you mean like this? :p

https://youtu.be/FFCfI4EaD0E
In the shots of the Jaguar at Farnborough (I saw just about every takeoff/landing from the tower) you may notice clods of earth etc flying up during takeoff, this being deposited on the runway and taxiway; most annoying and entirely unexpected the first time he did it. Fortunately they were able to clear it up every time to avoid ingesting it next time although there were no reports of any being ingested when they landed after the first rehearsal.

[Mogwi]

Funniest thing I saw on a grass strip was several dozen Mach 1 voles being ejected vertically as a Jumping Bean selected nozzles down on a short take-off in Sennelager. Cause was over-pressurisation of their burrows!

How I did larf!

Mog

[Baldeep Inminj]

Perhaps some slight thread drift here but sort of related...

The issue of power required to lift vertically without aerodynamic assistance is also causing huge headaches in the very latest aviation adventure - EVTOL's. There are some very bold claims being made by some manufacturers about the capabilities of their aircraft in terms of range/speed/endurance, but these are actually just aspirations and rarely based in fact and current physics. One of the myriad issues is the requirement to be able to lift and land vertically, as this requires huge amounts of power and it is currently depleting the batteries at such a rate that relatively little is available for the bit between take-off and landing. Some 'industry leaders' are saying their devices will have an endurance of 90 minutes, yet they cannot currently stay airborne for more than 15, due to the limitations of energy density provision by the latest batteries, and the take-off alone is killing them in terms of battery power available for the flight itself.

Great explanation here: https://www.sciencedirect.com/science/article/pii/S2542435121002051



Perhaps, in a similar vein to the originators comments, they need a detachable plug which jettisions when the EVTOL is at height and starting the transition to forward flight?...and no, I am not really being serious, but something does need to be done in order for this new technology to meet the claims being made about it.

[Lyneham Lad]

EVTOL's and battery drain on lift-off - one could amend glider-launch methodology by attaching the aircraft to a large helium filled balloon. Said balloon is attached to a winch, winch ratchet is released, up goes balloon and EVTOL. At a a suitable height, pilot pulls on the release handle and zooms away. Balloon is then winched back down ready for the next customer. Problems solved!

Hmm, maybe I should patent that... ;)

[sandiego89]

I particular enjoy all of the glossy EVTOL renderings that show attractive and fit professionals whisking off to their next meeting, or lunch at the country club...will be exciting when a few more robust Pax order their air taxi and our poor machine whirrs, whines and beeps....unable to lift off....

[pasta]

At a a suitable height, pilot pulls on the release handle and zooms away.
Which got me thinking... Do these things have an autorotation capability?

[Geriaviator]

Impressive RATO by the Starfighter was fitting sequel to the Me163 rocket interceptor of 1944 which can be seen on Youtube. Postwar the great Winkle Brown was cleared to fly it as a glider but also made an (unauthorised) flight using power. He recalled that the Komet was more a threat to the Luftwaffe than it was to the Allies.

[Video Mixdown]

Impressive RATO by the Starfighter was fitting sequel to the Me163 rocket interceptor of 1944 which can be seen on Youtube. Postwar the great Winkle Brown was cleared to fly it as a glider but also made an (unauthorised) flight using power. He recalled that the Komet was more a threat to the Luftwaffe than it was to the Allies.
That's what it reminded me of too. Mind, I think most of the exotic weapons tried by the Germans towards the end of the war were just a drain on scarce resources.

[chevvron]

Impressive RATO by the Starfighter was fitting sequel to the Me163 rocket interceptor of 1944 which can be seen on Youtube. Postwar the great Winkle Brown was cleared to fly it as a glider but also made an (unauthorised) flight using power. He recalled that the Komet was more a threat to the Luftwaffe than it was to the Allies.
:mad::oh:!!!!!!!!

[Baldeep Inminj]

Which got me thinking... Do these things have an autorotation capability?

No, they do not. They have fixed pitch props/rotors/fans and vary RPM to change thrust. If there is a total power failure then a ballistically fired parachute is the only way down, and you land where you land - the pilot does not get a say if it comes to this, as he will have just become a passenger.

And to the point of 'fit professionals whisking off to meetings' - it is absolutely valid. It appears likely that everyone will be required to provide their weight and dimensions before booking a flight - and no, I am not joking (is it even legal to ask that information in most Western countries?). EVTOLS will be extremely weight sensitive, so a couple of my 400lb North American colleagues (and we have a lot of them) might render the machine unable to fly. Imagine being the pilot telling a drunk 400lb Texas cowboy that he is too fat to get in...no thanks.

The idea of electric air vehicles whisking people across cities, cleanly and quickly, is a great one, but as with all things, the Devil is in the details. And there are a lot of details.

[NutLoose]

The most impressive set up was a line strung between two booms down the side of a ship for Normandy, a Piper Cub would fly alongside and catch it with a roof mounted hook, he could then fly back off it! Meet the Brodie system.

https://youtu.be/-dLJzVxu760

[Sue Vêtements]

Thanks everyone for the interesting replies

And the video took me back in time. I was there when they landed on the M55!

[Davef68]

VLs would also be affected by weight - in fact I recall that was one reason for the demise of the SHAR, in that recoveries with full weapons proved troublesome in hot conditions, and the proposed Pegasus upgrade was too expensive

[Mogwi]

Yes, VLs were affected to a lesser degree as free hover JPTs were lower that VTO JPTs. This where CRVL is a bonus. I believe the engine upgrade would have required major airframe work as the engine was physically larger. It was never particularly comfortable committing to a wet VL because if the water stopped flowing you would quickly cook the donk.

Mog

[NutLoose]

Plenhum burning reheat, that's what it needed... ;)

[Mogwi]

Plenhum burning reheat, that's what it needed... ;)

Now that really did burn the gas!

Mog

[fdr]

Plenhum burning reheat, that's what it needed... ;)

Now that really did burn the gas!

Mog

The pegasus design was pretty neat, but problematic to get much better performance out of. the nozzle design of cold-hot regions means messing with the fan efficiency would give a bit of a balance problem. The bypass ratio is 1.2, but the TSFC was not bad for its day at around 0.76. My own R&D took a 2.67 BPR and gave 4.3 BPR after a field mod to the fan, with a lower EGT and the same fuel flows, N1, N2. That would have suited a mixed flow to the rear nozzles with lower temps, and longitudinal balance by cold stream diverters. Getting higher bypass is not going to add more drag, the intakes have to be substantial for the low speed mass flow, so the diameter of the fan could easily have gone up to the 61" level of say a CFM56-3. With mod, the CFM56-3 would put out 30550 lbf but the installed weight would be higher, around 500lbs heavier; gotta go to Jenny Craigs. The CF34-10E would fit the same form factor of the AV8B, with some shoe horning, and would put out 26,500lbf for the standard EGT/fuel flows with a modified fan efficiency, both would use half the fuel flow for a given thrust (TSFC) of the Pegasus. I happen to like the flexibility that the Harrier gives, and it wasn't under built, as your tail ding would attest to down south in '82. Reducing the TSFC by half for around 25% more installed thrust would be worth the exercise machines. Now, making it low RCS would take some doing... that fan is a great reflector.

Higher bypass would have got rid of the hot gas ingestion issue in part, make some landings less exciting.