McDonnell Douglas Alternative Harrier Replacement.

[deathjester]

Wow!! What a wonderful concept - and so beautifully executed 

[kitnut617]

A bit more to what I've done with this, I made up some 'cold air ducts'

Here you can see I've added some deflector guides into the bend.  I did this because the insides of the ducts are quite visible



This is how it looked once all the sides were on.




I've also made up the hot exhaust pipe, times two.  One is a straight through and the other is as it's swivelled down.  They're a friction fit into the rear of the engine so I can pose the model either way although the doors will always be in the down position.



I made these by glueing some styrene to some tubes, this is supposed to represent stiffeners on the outside




It then gets to look like this






You can see the cold air ducts to good affect in these pics.

[kitnut617]

Robert,

I haven't read through all the other replies so forgive me if someone has already mention that it's like a Yak-41/Yak-141 but better looking. I can't wait to see it finished with markings applied.

Yes a little like it except I haven't gone with the dedicated lift engines at the front, the sysem works more like a Harrier's engine where the large fan is used 100% of the time for all modes of motion

[Go4fun]

This is coming along great and looks like something real world, not a Whiff.

[Captain Canada]

That thing is awesome ! Glad you resurrected her !

[kitnut617]

Thanks again guys, I'm really please myself with the result of all the work.  The next challange is to complete the u/c.

[PR19_Kit]

Looks a sight better than an F-35 too! They should have built it!

[aerofan]

Yes a little like it except I haven't gone with the dedicated lift engines at the front, the sysem works more like a Harrier's engine where the large fan is used 100% of the time for all modes of motion

After seeing some pics of it.  Would the cold air ducts have doors to streamline the fuselage? Also, would there be doors at the compressor section to allow for proper engine operation during level flight. Asking because the cold air ducts don't seem to add to the thrust in level flight or have I spoken too soon and should wait to see the progress of the build to answer this.

[McColm]

Great build, I hope my Mig 1.44 V/STOL build turns out as good as yours!!

[kitnut617]

Would the cold air ducts have doors to streamline the fuselage?

Yes, there will be five or six deflectors plates in this area, they would move from flat against the fuselage bottom to about 5 degress facing forward, pretty much like what the Harrier nozzles do.  I've got an added feature though, these deflector plates would be mounted on a 'gimballed' frame which can direct the air jet off to the sides.  My idea is that all the hovering flight controls will work through the three jet thrusts, yaw would be controlled by the hot exhaust nozzle 'rocking' side to side (like how the F-35 system works) but also by the rocking cold duct deflector plates. If the hot exhaust is pointing to the left, the cold air deflectors would point to the right.  Of course everything is infinitely variable.

Also, would there be doors at the compressor section to allow for proper engine operation during level flight. Asking because the cold air ducts don't seem to add to the thrust in level flight or have I spoken too soon and should wait to see the progress of the build to answer this.

Your question here I thought I had addressed further back in the thread but a quick review it would seem I only brushed on it so it would be appropriate to explain the whole idea of the propulsion system, because it will explain the other hovering controls operation.

I had long been thinking of how you could make a Harrier go supersonic and from reading various sources for info, the hang up was the engine and it's intakes. I have looked at and read about the various systems that were developed to make a jet hover, and my pet peeve is the systems that have all this extra equipment on board that is only used for the vertical take-off or landing.  The rest of the time it's just dead weight being hauled around and taking up lots of room for other things.  I'm also not in favour of the PCB system developed for the Harrier and P.1154 projects, I like the cold air/hot exhaust solution.  I also like the ramp style air intake system, it's about the most successful system used.

[kitnut617]

(I was getting fed up with the reply page jumping back and forth so I've continue in another post)

Even though the Harrier is one of my favorite aircraft I think it could be improved on.  In my opinion, the cold air and exhaust exiting where it does when the aircraft is in forward flight is not the most effecient way of doing it, although it was a very good solution for the time. A better way would be if the cold air/exhaust came right out the back and there are literary thousands of examples flying around today doing just that --- just look at any airliner!  So that was the genisis of the idea.

Then it was sorting out how to make a high bypass engine work for a hovering aircraft and a solution suddenly came to me after watching some airliners landing at the airport just when they put the engines into thrust-reverse.  One particular type has the whole rear half of the nacelle slide back to expose a slot in the side where the bypass air is deflected to blast forward.  My thoughts were there has to be something inside the nacelle that blocks off the bypass air flow for this to happen and that's when the solution to my system came about.

Now my engine is purely 'What-If', I looked at various engines that are available but nothing came in the range I was looking for.  My idea is that RR converted an Olympus 301 from a Vulcan B.2 (20,000 lb dry thrust) into a high bypass engine, with the bypass air producing another 25-30,000 lbs of thrust, but lets just say 25,000 lbs for the moment.  The operation into hover for this engine is very simple, using the same actuators that close of the bypass air flow out the back on the airliner engines, they would do the same here and at the same time some doors open in the engine tunnel upstream of the 'dams' to divert the bypass air down the cold air ducts (there's a very crude sketch in post #60 of this thread which shows my idea).

These cold air ducts are then used for all the other hovering controls, I haven't put them in yet on my model but there will be a couple of vents in the top of the fuselage directly above the cold air ducts. So a number of things happen simultanously, the hot exhaust nozzle starts to swivel downwards, the actuators block off the bypass air out the back, the doors to the cold air ducts open as does the small vents on the top of the fuselage (half opening).  The vent idea is so the air pressure in the cold air duct can be differentially controlled for pitch and roll. For pitch up, the vents would close off completely, for pitch down the vents open completely and for roll, one vent would open while the other closes.  And that basically is the idea.  BTW, there's no after burner in the system, I figured 45,000 lb of dry thrust is plenty --

[kitnut617]

Here's a couple of pics which show how the rear of the aircraft looks like when in forward flight (these were taken quite a while ago while I was still planning how the build would go)

[kitnut617]

Going further back in the build, because you would be able to see up inside the model once it's finished, I decided to put an engine in. The disc at the front is supposed to represent the rear of the fan static blades.





a size comparison



I put an engine tunnel in --



and then the engine slides in like this --






When I 'buttoned-up' the fuselage I glued the engine in further back in the fuselage so the exhaust pipe would be as short as possible, as you can compare with the finished exhaust nozzle photos I posted a few posts back.

[PR19_Kit]

More model engineering! Good stuff Robert! 

[Hobbes]

Agreed, I'm really enjoying this one.