Because the aircraft designer can use a higher aspect ratio for a conventional tail, too.

If you don't hold all the other variables the same, then you aren't measuring the effect.


I agree but that is the same as saying a conventional tail can provide the same stability with a higher aspect ratio. You are measuring aspect ratio impact, not tail configuration.


My belief is that the 36 tail is the same, but I don't have any evidence saying so. Get out the measuring tape!


Yes, they are, which is more common of newer designs these days. Higher aspect ratio is better aerodynamically but makes the structure more critical, especially for flutter.

You can always make a conventional tail of equivalent aspect ratio.

Mike C.

I'd say that incident does clearly demonstrate how poor the Eclipse avionics are.

I think we could both agree on a G1000 EA500

You're welcome.


It should be noted that SF50 has 4 such junctions due to being an X tail in reality, a conventional tail normally has 3.

If reducing junctures is the goal, then the best tail is a T tail which has only 2. All the highest performing sailplanes are T tails, perhaps at least partly for that reason. The Eclipse is T tail as well.

Mike C.

If it created more drag, they would have said that. They didn't. They said it "would tend to require increased weight". Engineering papers are nice in that there are usually no hidden elements. No extrapolation is required. If an effect exists, they'll tell you.[/quote]

Is there a scenario where weight increases and drag doesn't all other factors being constant?

The G1000 doesn't get into engine control (though it does do engine monitoring).

This issue was in the FADEC software, thus not related to "avionics".

Mike C.

They considered parasitic (or form) drag which is not caused by producing lift (thus unrelated to weight). You can make the tail out of lead and as long as it has the same shape, it has the same parasitic drag.

But from a system perspective, weight is ultimately drag from having to produce the lift to counter it. The authors of the paper assumed the reader understood that as it is one of the basic principles of aeronautical engineering and it doesn't have to be said.


They can't possibly enumerate the totality of effects from increased weight in every paper that mentions that issue (which is every paper on airplane design since weight is always an issue). For example, they didn't say heavier tails mean a CG shift, yet we all know that is true.

I think it is eminently reasonable they assume a reader who understands the impact of increased weight.


If the weight is added somewhere that changes the trim of the airplane to make it have less trim drag. Example, adding a weight in the rear baggage which makes your plane fly faster despite now being heavier.

If that is the case, your plane is just out of balance from optimum. If you can shift the CG back a bit at no increase in empty weight (relocate something), then you can fly even faster without the weight.

Of course, more rearward CG means less stability which can be countered, to some degree with larger tail surfaces. The issues are all intertwined, as you can see.

Mike C.

Mike C has a profound point. I wish I knew the pilot of the eclipse that had the diagnostic presence of mind to land at kmwd. In my opinion, he has not received enough props.

I love XKCD and this one in particular.

My fav Dilbert:



Mike C.

That might be the funniest thing I've ever seen on Beechtalk!

I'd say that incident does clearly demonstrate how poor the Eclipse avionics are.

I think we could both agree on a G1000 EA500

Speaking of the engine
I never noticed how much upward the engine seems canted. Or is it level inflight?
I was looking for a side view of it.
MC

This is the second funniest thing I've read on Beechtalk; first place goes to someone who made a cartoon video where the characters are arguing single vs. twin and one guy refers to the other guy's plane as "a plastic clown plane".

Oh yeah, you were right about the MU2 on all points. Same applies to Aerostars and their drivers...

Not badly 1,39M for new jet http://www.controller.com/listingsdetai ... 347997.htm

It will be worse in flight as the plane has to have some positive deck angle at FL280.

From the picture, it appears to be canted about 12 degrees. Assuming 3 degrees nose up at FL280, that's 15 degrees of misalignment with the direction of flight.

Doing the math, at 1800 lbs thrust, that's 1738 lbs forward and 465 lbs (!!) thrust vertically. At FL280, it likely doesn't produce 1800 lbs thrust, though, so the numbers will be scaled back somewhat. But still, hundreds of pounds of vertical force exerted due to the canted engine.

It will be interesting to see how much pitch trim changes with power.

Mike C.