JetPOD crashes on maiden flight, creater lost...

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

WHat "co-pilot/mechanic" ? I haven't seen one mentioned anywhere.

Where did you read about him?

[First time Juke]

Re: JetPOD crashes on maiden flight, creater lost...

Naturally in the internet concerning the case.

[First time Juke]

Re: JetPOD crashes on maiden flight, creater lost...

Last paragraphs here; http://thestar.com.my/news/story.asp...356&sec=nation

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

I've read that one before, but I didn't want to post that article because of the gruesome way the author describes the recovery of the pilot's body. That part of the text wasn't necessary, and was unkind to the family of the deceased...


The text mentions a co-pilot suggesting he go along, but nothing about him also being a mechanic. That's the part I haven't seen mentioned anywhere and was asking about.


The only new "news" I have seen is a local article (local to the accident site) stating that they are keeping the pilot's body at Taiping Hospital, and not letting the family bring him home to the U.K. until further investigations of the accident are completed.

Link: http://www.bernama.com/bernama/state...=433915&cat=nt


.

[AAFO_WSagar]

Re: JetPOD crashes on maiden flight, creater lost...

The description of the crash in the link Juke posted earlier is a gross example of TMI when it comes to reporting.. far too graphic!!

[First time Juke]

Re: JetPOD crashes on maiden flight, creater lost...

I've read that one before, but I didn't want to post that article because of the gruesome way the author describes the recovery of the pilot's body. That part of the text wasn't necessary, and was unkind to the family of the deceased...

The text mentions a co-pilot suggesting he go along, but nothing about him also being a mechanic. That's the part I haven't seen mentioned anywhere and was asking about.

Right the co-pilot could have been a mechanic..that was my assumption.

This was not very polite towards the inventor and his family I agree to explain all details.

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

Right the co-pilot could have been a mechanic..that was my assumption....

Ah. Well, let's not ADD any details to the accident info to keep facts accurate and rumors/mis-conceptions to a minimum, please.

[First time Juke]

Re: JetPOD crashes on maiden flight, creater lost...

Ah. Well, let's not ADD any details to the accident info to keep facts accurate and rumors/mis-conceptions to a minimum, please.

What diffrence does it make here..the point was that the pilot refused to take co-pilot with him since he was about to take off...and not taxi the plane. Wasn't this what Ice Pack assumed ?

[IcePaq]

Re: JetPOD crashes on maiden flight, creater lost...

My assumption is that he didn't take the other guy along because he only intended to fast taxi the plane and maybe move the elevator a bit to see what kind of authority it had but the design dictated that the huge amount of force necessary to affect any pitch change was more than enough to cause problems if the wing generated any amount of lift.

There have been similar accidents involving planes with main gear too far aft of the center of lift that ended the same way.

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

What diff does it make HERE? I believe that accuracy of info is VERY important at AAFO, and ESPECIALLY at AAFO.

ANYWAY...

All this talk of gear location and elevator issues being the cause ignores the fact that this is an STVOL, and is suppose to use some ducted jet thrust to lift-off. How do you know it's not a propulsion-related issue?


Too many potential culprits (shakes head).


Meanwhile, here's some ACCURATE info related to the issue:

TAIPING: No flight plan was filed for the maiden test flight of the Jetpod which crashed at the Tekah airstrip here on Sunday, killing its inventor Michael Robert Dacre.



The Civil Aviation Department said the test flight was not registered in the Civil Aircraft Register.



MCA vice chairman Datuk Ho Cheng Wang said the Tekah airstrip was no longer surrounded by jungles as in the old days.

“The airstrip is now surrounded by housing estates and who is going to be responsible had the plane crashed into some houses in the vicinity?” he asked.

The airstrip is not suitable for conducting test flights.



Taiping deputy OCPD Superintent Syed A. Wahab Syed A. Majid said since the airstrip was surrounded by housing schemes, advice from the police should have been sought.

“Although we are not empowered to approve or disapprove the maiden test flight, we would have studied the matter and given our views because we must also think about the safety of civilians in the vicinity,” he said.

[IcePaq]

Re: JetPOD crashes on maiden flight, creater lost...

I've been following the jetpod saga since it started and even sent an e.mail to about 5 years ago telling them what would they were up against if they used that configuration on the finished plane.

I actually found this forum while performing a search for a thread in another forum where I predicted it would pitch up and crash if it somehow generated enough elevator downforce to even lift the nose at all.

I'll try to dig up flight test data from other planes that had "too far aft" main gear that experienced dangerous pitch up because of the configuration.

I made an educated guess but it doesn't take a genius to see that the jetpod will experience violent pitch up once it goes fast enough to gain enough elevator authority to even lift the nose with that short arm and the fulcrum transfers from the main gear to the center of lift.

I'm actually surprised that he even got the nose up at all and I'll venture a bet that it happened at a very high rate of speed when it did.

On top of the main gear being too far aft, the engines are too high and will pitch the plane nose down under thrust requiring even more downforce from the tail so.....it's even possible that the plane pitched up AFTER he pulled power if he had any elevator in it while powering down the runway.

It's also obvious that the Jetpod would experience a nasty nose gear touchdown after the mains are down because of the main gear location.........unless the plan was to land with very high power setting and ducting mucho thrust downward near the front of the wing.....which would still make landings on a short field near impossible since I doubt jetpod can divert anywhere near the percentage of thrust downward required to counteract the short arm from tail to wing on an approach and still not have too much thrust propelling the plane forward such that it can decelerate.

The band-aid to tame such a configuration would be a high angle of attack while sitting on the gear much like what they did with the F7U cutlass or maybe a higher angle of incidence in the wing such as in the F8 which would eat into speed and efficiency unless it was also able to be adjusted in flight as the F8's wing is.

As the matter of fact, the F7u had main gear that moved further forward for take off than for landing.

I stand by my guess and challenge anybody to find a picture of a flyable plane with the main gear as far aft as the jetpod relative to the tail and the center of lift from the main wing.

The only flyable planes you will find with gear that far aft of main wing's center of lift will have canards up front or have an excessively high nose high attitude while sitting on the mains.

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

I'd have to know far more of the actual internal design and concept to venture a true argument, but there's a few points I can make:


--> The assumption is made that the plane was intended to pitch-up like a conventional design to achieve take-off. How you you know the aircraft wasn't suppose to achieve flight with a more level stance, ala B-52 and AN-124? Those aircraft both sit level at static and during take-off, yet manage to get off the ground just fine at said level attitude even with far-aft main gear locations.

The mentioned Boeing bomber has it's rear-located gear set WAY aft of it's center-of-lift and C/G, and I'd LOVE to see someone try to pitch up the Antonov with it's lengthy caterpillar-type gear arrangement. Neither machine requires a pitch-up maneuver to obtain flight, and as far as I know, neither has canards up front.


--> How does anyone not involved know if the unconventional jet thrust ports, located AHEAD of the main gear, were intended to provide the "push" the close-coupled elevator needed to lift the nose, or provide enough upward push to get it off the ground without said pitch-up?

--> Artist drawings available show very large flaps situated below the wing and above the main gear, with most of said flap appearing to be in front of those wheels. Perhaps those (along with the vertical thrust component) were to provide the lift to get it off the ground without the pitch-up maneuver you suggest.

Again, not enough detail has been revealed about this unique system to venture a true EDUCATED guess, and so using conventional aircraft designs as examples may not apply. Details of this thrust/flap system haven't been forthcoming, and possibly never will now.



--> And finally, the assumption is made again that the severe pitch-up and resulting loss of control happened while the gear was still on the ground, yet initial reports state that the plane had ALREADY left the ground, and had successfully reached 200 meters of altitude BEFORE the pitch-up occurred. The gear location would be a non-factor if this is the case.


I agree that a CONVENTIONAL aircraft with such a short-coupled T-tail would experience pitch problems at take-off, but then this is far from a conventional concept.

This is why I say, much more info of this one-of-a-kind design would have to be forthcoming BEFORE any form of real educated guess could be made by myself. What applies to apples may not apply to oranges.

[First time Juke]

Re: JetPOD crashes on maiden flight, creater lost...

I've been following the jetpod saga since it started and even sent an e.mail to about 5 years ago telling them what would they were up against if they used that configuration on the finished plane.

I stand by my guess and challenge anybody to find a picture of a flyable plane with the main gear as far aft as the jetpod relative to the tail and the center of lift from the main wing.

I bet that is the reason why Molt Taylor Aerocar looks how it does..the added tail actually shifts the CG dramatically from automode to aeromode.

I have not seen a single pic how the Jetpod looked like before the mishap.

[IcePaq]

Re: JetPOD crashes on maiden flight, creater lost...

The B52 gets around the aft main gear location with a main wing that is mounted extremely far forward to lift the front in addition to having huge flaps mounted right behind the engines.

Had the jetpod had the engines mounted under the wings acting on flaps the way the B52 does, there would have been no need for ducting thrust downward.

Sure it takes off flat but the B52 has more than enough length between the wing and the tail in addition to having lift far enough forward to lift the front without considerable downward pressure from the tail.



The An124 has a very long arm with which the tail can act in lifting the nose and the gear is not nearly as far aft in relation to the plane's center of gravity as in jetpod and it certainly does not take off flat.

It also has the engines acting on large flaps under the wings.

Neither of those planes has the engines mounted high forcing the nose down.

http://www.youtube.com/watch?v=KkQyet-mREg

I'll come back to this thread once the investigation is over and see whether my guesses were correct but further discussion seems to be headed toward an argument so I will only view this thread until the experts post thier findings on the incident.

[AirDOGGe]

Re: JetPOD crashes on maiden flight, creater lost...

Not correct about the engines blowing on the flaps to increase lift. That wasn't done until the C-17, and is why it's engines are mounted close-to and forward of the wing on shorter-than-usual pylons, rather than well below like the older aircraft.

On the Boeing, large gaps exist BETWEEN the flaps to allow the jet thrust to blow directly back. Said older aircraft's flaps weren't designed for hot exhaust to strike them.



If you watched many B-52'a take off, sometimes the rear wheels actually lift off before the fronts.

And the AN's engines are mounted well below the wings on tall pylons, so that their exhaust does not strike the full-span flaps.


And despite the forward location, the Boeing's wings are swept far aft, so the center of lift is much farther back than you state.


Having the engines mounted on top does not impede flight as much as you say. Having personally worked on NASA's QSRA research aircraft at AMES (the wind tunnel model actually), and having seen the actually aircraft make many successful take-offs, I can say that having the turbines on top of the wing works just fine. In fact, that aircraft gets off the ground in shorter distances than most.




Anyway, If you look at pics of the Jetpod, you can see that most of IT'S it's wing is also set well forward on the airframe, so the Boeing wing-location argument applies to it as well. Along with the large flaps and vertical thrust component, it should have no problem getting off the runway without a conventional pitch-up.


Along with JUKE, I too have not seen any real photos of the J-pod, only drawings. as such, NONE of us have any idea of the actual aircraft that was flown and lost, only drawings that show some detail but leave out so much more. Things could have changed since these were released:




Scholars familiar with this aircraft's design have already investigated and confirmed the wing layout as being capable of short distance take-offs, and since they have seen the details we haven't, I tend to trust their opinions:

The Jetpod operating principle of using a through-wing vertical thrust component, along with its unique wing-shape, have been confirmed by City University in London. City have confirmed that the aircraft can take-off or land in a distance of less than 125 metres (410 feet).

The rear-mounted gear location is obvious, so if the design wasn't intended to compensate for it, surely that point would have long-since been addressed and dealt with.


Finally, you are still ignoring the point that the plane may have already been in flight at the height of a 60-story building BEFORE control was lost, where gear locations and pitch-ups from the runway do not apply:

Witness statement:

"...on the fourth run, the jet took off into the air but at about 200 meters high, it shot vertically to the sky before veering to its left and then falling to the ground,"

If it had said that the pitch up to vertical flight had occurred while trying to leave the runway, then I might be agreeing with your viewpoints, but that doesn't seem to be the case here.



In any case, This has been a good discussion and I don't see it leading to any kind of unacceptable arguments. I have enjoyed the debate myself, as you offered some pretty good counter-points.


But I DO agree that waiting until further official investigation is completed is the next best step for this topic. Neither you nor I have enough real info to take it further. Of course, I've been saying that since I started this thread . As I like to say, IT'S ALL GOOD.


Take care, be well, and thank you for taking up the topic with me.