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Today's Engine Puzzler

Dear David,
After receiving criticism for your style of post and your moral character as well, you simply responded with an explanation and a sincere apology. Not only that, after realizing that ?perhaps? this was not the most popular way to approach problem solving on this forum, that you would change your ways in the future. These things indeed take a great deal of moral character! So, I tip my hat to you, good job, and have a nice day.
Sincerely,
Rick Meyer

Plus 1

with extra characters
 
Great job keeping an A model upright in that soft sand. Shows that you landed it right.

It looks like you have the Anti-splat nosegear mod. Does it have witness marks that look like it may have hit the gear on this landing?
 
It is good to finally to hear the solution to the problem, and it was a bit frustrating, but lets be fair here guys, Paul Dye has posted a puzzler like this in the past. Perhaps a different implementation as he stayed with the posts, but the same basic idea.
 
Lack of primer.

That or because it is a tipup-slider taildragger with a nosewheel.

Gee Bill, Is it the tail dragger nose dragger thing again? I guess I have time to decide on which side of the coin I will fall. Nose dragging or tail dragging :D

I do admit that with posts like this, my list of what to watch out for is growing.
 
Gee Bill, Is it the tail dragger nose dragger thing again? I guess I have time to decide on which side of the coin I will fall. Nose dragging or tail dragging :D

I do admit that with posts like this, my list of what to watch out for is growing.

If you make the wrong choice John, I'm not sure we can be friends anymore.
 
"You don't have a proven product until you have 500 units installed in 500 homebuilts by 500 amateurs."

So true, that.
 
If you make the wrong choice John, I'm not sure we can be friends anymore.

Well...... I suppose we will have to see.

It is good to know that there is a wealth of information available on the site and many who are ready to reach out to offer assistance. I feel, that I have a ways to go just starting out, but will continue browsing through the posts, especially on those items that impact my stage of construction. That and photos of flying aerospace vehicles. :D
 
Thanks for the reveal! Nice to know what happened. Just save the puzzlers for the 3rd half of the show ....
 
Whew !

I?m also about 8 hours into phase 1 with my 6A with duel Pmags.
I don?t think I?ve ever read a thread so fast in my life.
A very nice outcome that could have ended so much worse.:)
 
This is why you need to provide separate power and grounds to your P-mags!

This can't be stressed enough!

Again, please rewire your P-mags!

All aircraft without a dual buss/dual battery system have a single point of failure. I'm pretty sure the documentation does not require or suggest dual electrical busses if installing 2 Pmags, as most other EI systems recommend.

I might add that this is not the first time I've heard of lost power to Pmags causing the eng to quit after landing or on final.
 
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Imprints

Mojave River Landing
IMG_3049-1-mojaveriverlanding.jpeg

From the imprints in the sand it looks like the back wheels came off the ground and landed off to the side of the main track. The spinner, prop blades and air scoop all left an imprint in the sand.

Great job landing the airplane in the soft field! It is encouraging to see an upright off field landing of an -A model. How short was the landing rollout?
 
Observant dude!

From the imprints in the sand it looks like the back wheels came off the ground and landed off to the side of the main track. The spinner, prop blades and air scoop all left an imprint in the sand. ...
Brice, very observant. I had not noticed that. I'm guessing that this must have been quite a ride. David is either very good or very lucky or both!
 
In summation.....

I'll give you a D- in wiring skills, a B+ in problem solving, an F in forum decorum and an A+ in soft field landing techniques. A good learning experience all around. :D
 
All aircraft without a dual buss/dual battery system have a single point of failure. I'm pretty sure the documentation does not require or suggest dual electrical busses if installing 2 Pmags, as most other EI systems recommend.

I might add that this is not the first time I've heard of lost power to Pmags causing the eng to quit after landing or on final.

Walt,

No, the P-mags do not need a dual buss because they will operate independently in the event of an electrical failure.

The problem here is the OP turned off the P-mags and didn't realize it until he was on the ground. Had he not touched the P-lead, or turned it back on, the engine would have started up after he lowered the nose and his RPM's came back up.

That is the beauty of the P-mags, if installed correctly, as described in the manual, there wouldn't have been an issue.

This isn't the first time I have heard of people wiring them incorrectly. This is always a surprise to me as this is a critical system and yet builders continue to go against the advice listed in the installation manual.
 
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Haha I loved the puzzler. And what an amazing story about a forced landing with a very good ending. It was amazing to see that nosewheel plowed into the sand without a noseover.

Sure, I was a little frustrated like others to think I'd be waiting a week for the answer, but jeez not mad about it or anything. Hey we're a community here, and anyway who didn't love Click and Clack and their weekly puzzler?

I am inspired by this as I have had some puzzlers over the 20 + years flying my RV-6; I'll maybe post them in upcoming days. Nothing so dramatic as an engine-out landing in the desert, but still. And I'll be sure to have the answers right at hand - David learnt that lesson for me :eek:
 
I can see both sides of the lesson here. But at the end of the day it?s all about learning, and in my book the op gets an a+ for both the landing and the learning. Are we not all intrigued by the cause ? And we will all remember the lesson by being intrigued. Thank you for both
 
I shut everything off and made a forced landing on the sandy bed of the dry Mojave River. Fortunately I landed into a good headwind, the sand was firmer than usual because of recent rains, and I held the stick full back, so the nosewheel didn't touch until I had come to an almost complete stop. The aircraft was undamaged.

David

David, your very interesting story has prompted much worthwhile discussion and debate about the merits (or not) of the PMag. Beyond that, what seems to be fascinating posters is how you managed to land a nosegear RV in such soft sand without buckling the nose gear and tipping over. I, like everyone else, am absolutely amazed how deep that nosegear is in the sand. I am imagining that if you had your nose gear fairing on the added resistance in that sand might have produced a different outcome.

Can you please provide more detailed information on your landing, particularly the last seconds. Did the tail rise up and threaten to go over. Did the main wheels come off the ground. Did the prop strike the ground. And finally, as asked by some-one else, were there witness marks on the nose gear indicating that the AntiSplat brace had come into play.
 
Good post

David,
Good post, thanks for sharing, and I liked the puzzler.

As to forum practices and decorum, to be honest I'm kind of disappointed in the tone of some of the responses here. The worst thing this community can do is fuss at someone for both being creative and posting their choices/mistakes for all to read. It is always a risk to the ego to share things like this, and I think many of the respondents should have been more polite to David. Being aggressive is not going to inspire more compliance to your version of how the forum should go - it's just going to keep people from bothering to take the time to write at all and then we'll all miss the chance to learn. Please be careful about that, and be thankful to David for choosing to share his experience.
 
Walt,

No, the P-mags do not need a dual buss because they will operate independently in the event of an electrical failure.

The problem here is the OP turned off the P-mags and didn't realize it until he was on the ground. Had he not touched the P-lead, or turned it back on, the engine would have started up after he lowered the nose and his RPM's came back up.

That is the beauty of the P-mags, if installed correctly, as described in the manual, there wouldn't have been an issue.

This isn't the first time I have heard of people wiring them incorrectly. This is always a surprise to me as this is a critical system and yet builders continue to go against the advice listed in the installation manual.

I do not believe this is correct. The P-Lead (kill switch) was wired to a standard aircraft key switch, as long as the key switch was in the both position the P-Mags should have worked with enough RPM. You are always going to have multiple single points of failure when they are wired like the P-Mag manual. If any of the following components fail you would have the same result: Master Relay, Master Relay control wire, any of the ring terminals in the control wire wiring, Master Switch, Master switch ground wires.

Rob Hickman
N402RH RV-10
 
I was an early adopter of PMags and had my share of issues. Fortunately, they have addressed the issues since then.

It hasn't been mentioned explicitly so I'll say it here. PMags only generate their own power above a certain RPM, I believe it is around 1200-1500 RPM.

Therefore, PMags require ship's power to start an engine or operate at low engine RPM.

It is also important that pilots realize in the event of an electrical failure (as Rob mentioned above) you must keep the engine RPMs up at least 2000 RPM or higher, even on approach.

As mentioned in the Puzzler, pulling back power to a lower engine RPM during stall practice would cause both PMAGS to fail. Makes sense.
 
...
It hasn't been mentioned explicitly so I'll say it here. PMags only generate their own power above a certain RPM, I believe it is around 1200-1500 RPM.
...

Marc, that must have been a really early model then...

I can assure from tests that the latest 114 models quit somewhere around the 800 rpm range. At the same time, flying/gliding at reasonable speeds you will never see below 1000 rpm (provided there is no mechanical or other similar malfunction/blockage).
So that limit is really mostly relevant during rollout, taxi and of course startup, which is impossible without external power.
 
Hi Bernie, it has been a while. Your numbers are certainly better than mine. :)
 
Regarding the question about roll-out, I paced off the distance from when the tracks first appeared on the sand until I came to a stop, and it was 200-250 feet. I had the good fortunate of a strong headwind (more than 20 kts at altitude, uncertain of what it was on the ground but it was definitely blowing as the desert often does in the spring) and sand that was firmer after a recent rain. I don't recall the back wheel coming off the ground during rollout. Off roaders had left tracks in the river bed as well, which might be misleading. The aircraft had come to very nearly a complete stop by the time the nose wheel touched the ground and promptly dug in. I was in a five-point harness, but recall very little force coming to a stop, and no tail rise. There is a small black mark between the bottom of the anti-Splat and the nose leg, indicating possible contact of the two, but no scratches, chipped powder coat, or visible bends.

I discussed the possibility of a teardown with two mechanics and concluded it was not necessary. I do not want to debate this decision in a public forum and would kindly ask for others to PM me if you wish to critique my choice.
 
I agree with almost everything Bill said but disagree with one point of his analysis.

Walt,
The problem here is the OP turned off the P-mags and didn't realize it until he was on the ground. Had he not touched the P-lead, or turned it back on, the engine would have started up after he lowered the nose and his RPM's came back up.

I had turned off one of the two PMAG switches, most likely in turbulence before the event, though possibly while troubleshooting or as pilot error at the end of testing it during run-up. The other PMAG switch was in the ON position, and the key was in the BOTH position.

I am convinced the root cause was the bad crimp in the power wire between the main bus and the PMAG switches causing intermittent loss of main power to both PMAGs.

I believe that if I had lowered the nose sufficiently, the engine would have started up again based on the PMAG internal alternators. During a subsequent ground test, I found my left PMAG alternator runs down to 850 RPM and the left down to 780 RPM, which is consistent with expectations. By the time I attempted lowering the nose, I was too close to the ground to do it very aggressively or for long enough to manipulate the power and mixture settings while doing so.

It is also possible that the engine would have restarted better with the mixture briefly at cutoff, as in the normal starting procedure.
 
Thank You

David: Thank you for the kind word's!

Glade to hear ever thing is going forward, FLY SAFE

Jack Vandeman
 
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