Today's Engine Puzzler

[BJohnson]

Originally Posted by DavidHarris

Mojave River Landing

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?

[rv8ch]

Originally Posted by BJohnson

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!

[PilotjohnS]

Is it time for an engine tear down and inspection since prop hit the sand?

[ronschreck]

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.

[N941WR]

Originally Posted by Walt

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.

[rv6n6r]

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

[Hitt7A]

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

[Captain Avgas]

Originally Posted by DavidHarris

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.

[JordanGrant]

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.

[N402RH]

Originally Posted by N941WR

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