Ok, what about the BD5

"J.Kahn" wrote in message
...
Juan Jimenez wrote:

"J.Kahn" wrote in message
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The lack of crashworthiness inherent in the BD 5's configuration makes
engine reliability really critical. In the end the jet version is
probably the safest one due to the better reliability of a turbojet.

Actually, both of these statements are incorrect.

These two pictures show what's left of a Canadian BD-5 that landed in a
raspberry patch and essentially tore itself apart.

http://www.bd5.com/Canada/Canada01.jpg
http://www.bd5.com/Canada/Canada02.jpg

The man holding the pieces is the builder and pilot. He walked away.
About 30% of accidents involving BD-5's are fatal. 23% of RV-6 accidents
have been fatal, and that's not counting the fact that some of those
accidents had more than one victim. You can verify that yourself on the
NTSB web site.

The Microturbo TRS-18 that is most commonly used on the BD-5J is a very
finicky engine in many respects. For example, any minor deviation on fuel
pressure can cause the engine to shut down. The fuel pumps are very
critical components, which is why at least one of the operators is
heavily involved in designing replacement components and reengineering a
portion of the fuel system to increase reliability in this area. The
irony is that even though BD-5J's are mostly used for homeland security
as cruise missile surrogates, Microturbo, with facilities in Grand
Prairie, TX, refuses to cooperate. They won't even sell parts, directly
or through the military.

I see your point Juan, although I could probably spin that around and say
it has a "76% higher fatality rate than an RV-6!"

LOL! We have another statistician in the house. God help us.

Obviously you're dead as a doornail in a stall spin accident in either
airplane. What would be interesting to see is the survival rate of BD-5
vs other homebuilts in a controlled forced landing, which when you get
down to it is the key issue that I would worry about.

I've had several friends who had engine issues and had to do forced
off-field landings. All of them walked away. I have not done the statistical
comparison, and frankly I don't have the time to find the data and run the
numbers. Maybe someone else would like to try that. The ones who have not
walked away wind up in that situation because of their own doing. For
example, a BD-5TP pilot who is doing flight tests out at Mojave and then,
out of the blue and only a few hours into phase I, decides to come back to
his home field in a dense urban area, where there are no options if you lose
the engine on takeoff. The result was regrettably predictable.

I would think the ideal engine would be a properly developed wankel.

If you added the word "installation" to the end of that sentence, then I
would agree 100%. There is a BD-5 sitting in England with a Midwest Rotary
engine. It's been ready to fly for quite some time (and actually flew with
another engine). The CAA in the UK has essentially reached the conclusion
that UK pilots are not good enough to fly the BD-5 and have refused to allow
the aircraft a renewal of the permit to fly. The problem with a rotary is
the same as with other engines in the confines of the BD-5 engine
compartment -- cooling. From what little I know about these types of
engines, they generate a lot more heat than regular piston engines, and that
places an even higher burden on heat dissipation, which the BD-5 is simply
not very good at. Getting rid of heat on a BD-5 is probably one of the most
demanding tasks for the builder.

Juan



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Posted via a free Usenet account from http://www.teranews.com

J.Kahn wrote:
...

I would think the ideal engine would be a properly developed wankel.


You'd think that for any number of airplanes but where are they?

Rotax is selling a wankel now, maybe it will be successful.

--

FF

wrote in message
oups.com...
|
| J.Kahn wrote:
| ...
|
| I would think the ideal engine would be a properly developed wankel.
|
|
| You'd think that for any number of airplanes but where are they?
|
| Rotax is selling a wankel now, maybe it will be successful.
|
| --
|
| FF
|

Excuse me for jumping in here but I saw a wankel that a guy was
developing in Comanche, Ok. back in the '80s. He had a BD-5 in his shop
and was planning on using the wankel engine. It was a single rotor
design with enough power for the BD-5. His problem was high fuel
consumption. Exhaust temperature was another concern he had also. I
don't think he ever solved the fuel consumption problem.

The Mazda wankel actually had three times the CI that they advertised
according to an article I read at the time.

--
Jarhead




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"J.Kahn" wrote

I would think the ideal engine would be a properly developed wankel.

I would not think so. Waste heat has always been a problem for wankels, and
getting rid of that much heat from that tight engine compartment.
--
Jim in NC

"Morgans" wrote in message
...

"J.Kahn" wrote

I would think the ideal engine would be a properly developed wankel.

I would not think so. Waste heat has always been a problem for wankels,
and getting rid of that much heat from that tight engine compartment.

Exactly.



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Posted via a free Usenet account from http://www.teranews.com

On 1/4/2007 12:37:26 PM, "J.Kahn" wrote:
Whome? wrote:
Thousands of people instantly fell
in love with it immediately when it was introduced in what, the late 1060s.


Yeah I heard that William The Conqueror put down a deposit right after
invading England and was screwed by Bede in 1069...

Just teasing; that sort of typo is just too tempting...

Bottom line is the airplane, while a brilliant design, has always
suffered for lack of a really reliable powerplant that was light enough.
The lack of crashworthiness inherent in the BD 5's configuration makes
engine reliability really critical. In the end the jet version is
probably the safest one due to the better reliability of a turbojet.

Add in the fact of size, the nasty stall behavior with an 80mph stall
speed with the original 64-212 root airfoil (!) (see:
http://www.bd5.com/reprofile.htm ). Even with the reprofiled airfoil the
stall is still 60 which means you touch down at 70 and you really don't
want to do that in a plowed field after the belt on your Honda lets go.

So, you have an airplane with a market limited to those with high risk
tolerance and at the same time willing to do a lot of tinkering, which
is pretty small.

For someone that really wanted that configuration, the Mini Imp was
probably a more practical choice.

John


Yeah, that's another thing that I'm sure escaped most of the early buyers.
Even with the later wing modifications, for such a small airplane, it has
some really considerable runway requirements. William The Conqueror would
have probably needed to go with floats.



--
Whome?

It is interesting that we often look at a design approvingly, only to talk
about the lack of a suitable powerplant.

I find this perverse, as it acts like the powerplant isn't part of the
design.

It's a good looking little plane..The rotax 912uls should give this plane a
real boost in performance .Always wanted one but the stall speed was way too
high for me.A stall of 40knts would be great but no dice.
"anon" wrote in message
m...
It is interesting that we often look at a design approvingly, only to talk
about the lack of a suitable powerplant.

I find this perverse, as it acts like the powerplant isn't part of the
design.

I thought so too. It turns out the engine is too wide and too heavy, and the
fact it is watercooled adds even more complexity. So far, I haven't seen a
single BD-5 built with a 912.

"wesley maceaux" wrote in message
...
It's a good looking little plane..The rotax 912uls should give this plane
a real boost in performance .Always wanted one but the stall speed was way
too high for me.A stall of 40knts would be great but no dice.
"anon" wrote in message
m...
It is interesting that we often look at a design approvingly, only to
talk about the lack of a suitable powerplant.

I find this perverse, as it acts like the powerplant isn't part of the
design.








--
Posted via a free Usenet account from http://www.teranews.com

"wesley maceaux" wrote in message
...
It's a good looking little plane..The rotax 912uls should give this plane
a real boost in performance .Always wanted one but the stall speed was way
too high for me.A stall of 40knts would be great but no dice.

My father had a friend that owned one and he loved it. I'm not sure what
powerplant he used, but the fact that he probably didn't weigh over 160lbs,
was an Air Force pilot, and built light - probably helped the cause.

I think a lot of Cessna 150/172 guys found more they could handle in the
BD-5, especially after losing an engine. I think if more BD-5 pilots were
less concerned about getting back to the airport after an engine failure and
more concerned with maintaining airspeed, we'd have a few more BD-5 pilots.

Do the stats back that up in any way?

That said, designing around an unproven engine is probably a bad place to
start. Designing around an engine that hasn't been produced, probably a
bigger problem. I forget the details. What did the prototypes fly with?