Question to you 650 guys on Vne

I was just perusing the performance specs on the Zenith site, and noticed with a Jabiru 3300, the  "75% Cruise @8000 ft (TAS)" is listed as 160mph. The next line says Vne is 160mph. Imma assume that is supposed to say (IAS), because I ran across an online TAS calculator that yielded 160mph @ 8000 ft from an indicated airspeed of 138mph. What is the story on this? What if you pushed it to 162mph @ 9000 ft TAS, but you are still indicating 138mph? Is it the general assumption that you are safe as long as the IAS is below Vne? 

Also, what does the ASI look like for your plane with the green arc/yellow arc locations? Is there a specific model you buy to install recommended by Zenith?

Thanks for any answers

George

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Permalink Reply by Ian Robb on July 29, 2020 at 9:45am

VNE is usually listed as IAS. However, VNE is actually limited by TAS, more than IAS. Vans has some good reading on the subject. https://www.vansaircraft.com/wp-content/uploads/2019/01/hp_limts.pdf

Permalink Reply by George Burns on July 29, 2020 at 11:46am

Thanks! I'll dive into this during lunch.

Permalink Reply by David Krakowsky on July 29, 2020 at 10:52am
I don’t think you need to worry about a 160 mph vne
Zenith is notorious for exaggeration on their specs
I’m lucky to see 110 mph on a good day on my 601XLB
Permalink Reply by George Burns on July 29, 2020 at 11:47am
Permalink Reply by David Krakowsky on July 30, 2020 at 7:54pm
The only mod you left off was a rocket assist!
Permalink Reply by George Burns on August 1, 2020 at 5:00pm

The only unreasonable one is the retractable gear. But my question still stands, because this guy did it. It exists. So IS he in danger? Notice his altimeter was I believe reading in the 4000 range. If he headed on up to 8 or 9000, would his plane disintegrate on the first unseen pocket of turbulence? How fragile is that "B" modification? 

Permalink Reply by christopher fryatt on August 3, 2020 at 8:41am

Each design has an envelope of operation. The designer provides the load envelope of what's shown in plans. You couple exceed recommended limits and yes you have become a test pilot, id wear a chute and find some generous insurer for life insurance ( of course the T.P. may not care about family, certainly little respect for those below )

Permalink Reply by George Burns on August 3, 2020 at 10:48am

I agree with everything you are saying. I guess what I'm getting at is, it just seems "sketch" as the kids would say these days. And I need look no further than the design and performance specs on the CH-640 to show you what I mean. Max Cruise speed (Vc) is listed at 160mph, while Vne is listed @ 175mph. That's a 15mph safety buffer. MY POINT IS..... there IS no such buffer for the 650. 

http://www.zenair640.info/performances--specifications.html

http://www.zenithair.net/specs-ch650/

Note* NOW I SEE IT!!! The max cruise for the 650 is listed @ 138mph. Then they throw that 75% cruise @ 8000ft = 160mph TAS line in there. Which is what got me asking the question in the first place. I think Ian Robb has the most appropriate answer here. That 160 TAS is the crux of the issue. 

Permalink Reply by David Krakowsky on August 1, 2020 at 6:58pm
Hi George
I’m not following your question.
Who, what, why, when, where???
I own a 601XLB that was factory built by AMD, who are no longer in business.
The 601/650 are not usually able to attain those air speeds. There may be a couple of high power planes that exist that may be able to reach those speeds, if there are I would hope they would join in the conversation.
Dave
Permalink Reply by David Krakowsky on August 3, 2020 at 2:41pm
Say hello to Gracie
Permalink Reply by George Burns on August 3, 2020 at 8:02pm

I named my 3rd child Grace. Luckily, nobody her age knows enough to tease her about it.

Permalink Reply by Jay Carter on July 30, 2020 at 6:36pm

If you see 160 mph in a 601/650, you have other other problems to worry about.

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