Grimes Rotating Beacon

nyoung

nyoung

Pre-takeoff checklist
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Aug 5, 2008
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364
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Cary, IL
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Display name:
Nathan young
Hi All. The Grimes Rotating Beacon in the Cherokee had begun to spin very slowly (if at all). Plane is in for annual, so I decided to see what was wrong with the beacon.


  • I hooked the beacon up to a 13.8VDC source with an ammeter in series and found that when stalled, the beacon was pulling 2.2 to 2.4Amps!
  • Next, I found one of the gears that mates with the worm gear to be a bit mis-shapen, I filed that down slightly, and the beacon began to spin faster, and at less current. About 1.7A.
  • LPS'd the gears and got it down to 1.4A, while simultaneously improving rotation speed.
  • I was about to give up (happy that it was working again), but instead decided to use brake cleaner and a toothbrush to clean all the gears, then re-LPS. Wow! What a difference. The thing spins like a helicopter rotor, and only 0.6 Amps draw. Nice!
(all the current/amps figures are without the light installed - motor only).

Replacement LED beacons are a few $hundred, and I've heard that an overhaul of the Grimes is $600. So, I'm quite pleased my 2 hrs of goofing around saved that money. Hopefully this info can/will help someone else on POA.
 
It's good when things go that way!! I'm the same way. What does it hurt to try, Right!
 
Those LED ones look sharp.
 
I got rid of mine( rotating beacon) because of the whine heard through the radio.
Whelen Led, it's like a fricking laser beam on the tail ,0.8 amp draw, no noise, good for 20,000 + hrs ,Down side --$680
I'll relace the position and the landing lights with LED's next.
 
nyoung said:
Replacement LED beacons are a few $hundred, and I've heard that an overhaul of the Grimes is $600. So, I'm quite pleased my 2 hrs of goofing around saved that money. Hopefully this info can/will help someone else on POA.
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I would NEVER NEVER do this on a certificated aircraft, but I've got this friend Ernie that went to an outfit called Jameco Electronics (San Jose) that stocks damn near any size 12 volt motor you can imagine to replace the one that burned out (probably locked rotor, just like you measured). Ten bucks.

Jim :yesnod:
 
ScottM said:
Does that require an STC? I would like to do that to my Cherokee too.
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Yes and the paper work comes with the package,

comply with FAR 43.(B ) and yer good to go.
 
weirdjim said:
I would NEVER NEVER do this on a certificated aircraft, but I've got this friend Ernie that went to an outfit called Jameco Electronics (San Jose) that stocks damn near any size 12 volt motor you can imagine to replace the one that burned out (probably locked rotor, just like you measured). Ten bucks.

Jim :yesnod:
Click to expand...

I would never admit to having had anything to doing that, especially with a Globe motor of similar dimension and shaft size. Nope, not me.
 
Can anybody point me to the chapter and verse of the FAR that gives the technical specs for the rotating beacon ... angles, candlepower, and all that stuff?

I'm getting ready to do a Kitplanes article to show how to make an LED true "rotating" beacon for less than $50 in parts and it would be nice to be able to give the technical specs that it has to meet.

I don't know how Grimes does theirs...is it a flasher or truly rotating in a sense? My idea is to have three of them -aft and two sides - and "rotate" them by flashing in sequence (left, aft, right, left, aft, right...)

Comments appreciated. :cheerswine:

Jim
 
weirdjim said:
Can anybody point me to the chapter and verse of the FAR that gives the technical specs for the rotating beacon ... angles, candlepower, and all that stuff?

I'm getting ready to do a Kitplanes article to show how to make an LED true "rotating" beacon for less than $50 in parts and it would be nice to be able to give the technical specs that it has to meet.

I don't know how Grimes does theirs...is it a flasher or truly rotating in a sense? My idea is to have three of them -aft and two sides - and "rotate" them by flashing in sequence (left, aft, right, left, aft, right...)

Comments appreciated. :cheerswine:

Jim
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Why does it have to "rotate"? Why can't you just have an omnidirectional flash tube? Also, I would think that having 3 flashers 120 degrees apart would leave some "blind" spots in the "rotation".

FWIW, the Whelen beacon is a flasher. No rotation, simulated or otherwise, involved.
 
Greg Bockelman said:
Why does it have to "rotate"? Why can't you just have an omnidirectional flash tube? Also, I would think that having 3 flashers 120 degrees apart would leave some "blind" spots in the "rotation".

FWIW, the Whelen beacon is a flasher. No rotation, simulated or otherwise, involved.
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You did read that I was going to design it with LEDs, yes? LEDs don't use flashtubes.

Why rotate? Several reasons...for one, the power driver only needs to be 1/3 as big if I am only driving one LED at a time. Two, the coolness factor (if it looks cool ...). Three, I can use less expensive LEDs if I only do one direction at a time rather than having to do lots of candlepower all at once.

I believe that there is a "forward hole" in the beacon spec, which is why I wanted to look it up. That forward hole is there so as not to blind the pilot that has a rear window.

Do you have the FAR number?

Jim
 
Tom-D said:
Yes and the paper work comes with the package,

comply with FAR 43.(B ) and yer good to go.
Click to expand...

Why would changing from incandescent lights to LEDs be considered a major alteration? I'm not an owner so I would have figured this to be just a 1-1 swap in this instance. Educate me.
 
Greg Bockelman said:
Yeah, right.
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If you are thinking it's difficult, it ain't. It's just paper work.

buy the light, it comes with a STC to be applied to aircraft that isn't your make or model.

you fill out a 337 and in block #8 you simply say you are installing the light IAW the STC instructions.

then you write a cover letter to your A&P-IA's PMI, asking for a deviation to the STC to install it in your aircraft.

when the FSDO signs block #4 it becomes the authorized Data to install IAW block #8.

Do the paper work before you install, that is why it is call a pre-approval.
 
Jaybird180 said:
Why would changing from incandescent lights to LEDs be considered a major alteration? I'm not an owner so I would have figured this to be just a 1-1 swap in this instance. Educate me.
Click to expand...

because the modification is not in the type design.

any modification requires approval in one manor or other.
 
weirdjim said:
Can anybody point me to the chapter and verse of the FAR that gives the technical specs for the rotating beacon ... angles, candlepower, and all that stuff? Jim
Click to expand...

It's not in the FARs, it is in the appliance design/engineering. Certified IAW FAR 21
 
Tom-D said:
It's not in the FARs, it is in the appliance design/engineering. Certified IAW FAR 21
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Nope. I finally found it in FAR-23. It is the most gobbledegook reg I've ever read, but it is there. 400 candlepower directly abeam dropping to 20 candlepower at +/- 75° from the horizontal. It goes on further to say that there can be a solid angle of blockage of about +/- 15° across and up/down which should account for the little black blocking strips on the flashers to keep it out of the pilot's eyes.:

"The system must consist of enough lights to illuminate the vital areas around the airplane, considering the physical configuration and flight characteristics of the airplane. The field of coverage must extend in each direction within at least 75 degrees above and 75 degrees below the horizontal plane of the airplane, except that there may be solid angles of obstructed visibility totaling not more than 0.5 steradians."

​
First FAR I've ever come across with an integral as part of the specification, even a trivial one like this.

ec28se91.018.gif

​
Jim
 
nyoung said:
  • LPS'd the gears and got it down to 1.4A, while simultaneously improving rotation speed.
Click to expand...
hm...what's the difference between LPS and the Radio Shack electrical contact cleaner? And which version of LPS?

I've got a related problem - the motor is good, the bulb is new, but no light. Perhaps a bad wire someplace but I don't know where. Any suggestions?
I'm seriously considering replacing the 40 yr old Grimes with the Whelan strobe back there. Would really like the LED but $680 & install is out of the budget right now.
 
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ll the engineering has been done. The MINIMUM required by the Faa for the birth date if your airplane;
http://www.whelen.com/_AVIATION/assets/Anit-Collision%20Systems.pdf
The Faa has granted Whelen PMA approval to design and sell it's products for use on Certified birds, this means the design data of the light/mount/appliance has the Faa's blessing. In most cases the Whelen (or Aeroflash) replacenent does a better job the the part being replaced...Faa can't gripe about that!
Exceptions are noted on the site as "not for Certified Aircraft use". Most IA's will sign it off as a Minor repair. Note: Per 43.13B if the replacement beacon is on the rudder ( as opposed to the vertical fin) you need to verify the rudder balance prior to signing off the install.
Of course you could do the whole 3-point strobe install and get rid of the strobe for good...


Chris
 
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I used LPS#1, which is supposed to lubricate, but not leave an oily film (which would attract dust).

Regarding your beacon. IMHO, it is probably better to have a bad light than a bad motor...

On my Grimes beacon - there was (1) +12V wire and (1) ground leading into the case. Taking the bottom-half of the assembly apart, I found that the ground wire attaches to the case of the beacon. The +12V wire splits into (2) pcs one of which goes to the motor. The other goes to a grommet-like pass through to the light bulb assembly. If you take the beacon out of the plane, it should be relatively easy to see if one of the wires or connections are broken.

If you have a multimeter, you could also probe around a bit to make sure that 12V is getting to the light. Or to see if there is a short between the light terminal and the case.






murphey said:
hm...what's the difference between LPS and the Radio Shack electrical contact cleaner? And which version of LPS?

I've got a related problem - the motor is good, the bulb is new, but no light. Perhaps a bad wire someplace but I don't know where. Any suggestions?
I'm seriously considering replacing the 40 yr old Grimes with the Whelan strobe back there. Would really like the LED but $680 & install is out of the budget right now.
Click to expand...
 
Big question, who is going to return this to service. ?
 
Tom-D said:
Big question, who is going to return this to service. ?
Click to expand...

If your question is directed at me, it's the A&P that's been working on my cherokee for 10+ years. I provide the parts & checkbook, he does the work.
 
Tom-D said:
Big question, who is going to return this to service. ?
Click to expand...
Tom;
If this was a reply to my post the answer is the A&P/IA. Evidently they feel this is a minor change using PMA'ed replacement parts meant for replacing the parts they replaced.:idea:
One of the neatest replacements we did was on my Grumman AA1B. We removed the 3rd (defective) flasher and inclandesant base/bulb. We then pulled a HT cable thru the rudder post to the beacon location and the other end went to the space aft of the forward rudder mount bulkhead where we mounted the A490 strobe power supply. Aeroflash makes a strobe head (Aeroflash PN073-0141) that fits INSIDE the short little "jelly jar" with a silicone press fit base. The result was great! WAY more light and as cheap as replacing the flasher alone. All PMA approved parts with same form, fit and function. A 337 was done and sent to OKC...that was 6 years ago.

Of course; Weirdjim's answer works too:cheerswine:


Chris
 
My question was directed at post #1, He took it apart, cleaned it, and reassembled it.
who's going to return that maintenance to service?

and how are they going to comply with FAR 43.5 and 43.9

Choose your words carefully, IAW 43.2
 
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weirdjim said:
"Why, it's been like that ever since I bought the airplane."
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Then FSDO will want to see you and your logs at FSDO, because they will have a few questions.
 
Tom-D said:
No worries, the logs will tell all.
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Oh, don't we wish that the logs told all.

I know of some airplanes (luckily, none that I fly) where there has been some pretty major stuff done by unqualified people and you won't hear a peep out of the logbooks. :frown2:
 
flyingcheesehead said:
Oh, don't we wish that the logs told all.

I know of some airplanes (luckily, none that I fly) where there has been some pretty major stuff done by unqualified people and you won't hear a peep out of the logbooks. :frown2:
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When the FAA sees that the maintenance was completed and no entry was made the owner has a problem, as does the A&P-IA that signed off the last annual.

when the entry was made that entry may be the incriminating evidence that the FAA needs to make its case.

it is just a matter of proving who did what when.
 
Tom-D said:
When the FAA sees that the maintenance was completed and no entry was made the owner has a problem, as does the A&P-IA that signed off the last annual.

when the entry was made that entry may be the incriminating evidence that the FAA needs to make its case.

it is just a matter of proving who did what when.
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So - Let's say there was a hangar rash incident that crushed a wingtip. Plane's owner gets a wingtip from a salvage yard, paints it himself (hopefully for him, well enough to avoid detection), and installs it.

How is either the FAA or the A&P/IA going to know that it happened, or who did it? If the plane is sold, how is the next owner going to know?

Sadly, there is WAY too much of this going on out there. :frown2:
 
Agreed Kent.

There's also way too much, "We can't allow you in our shop for insurance reasons, no matter how well you know how to turn a screwdriver and follow simple directions," too.

I keep hearing these stories of the mythical IA who will work with owners. We haven't found one yet, and three shops we've approached simply refuse to do owner-assisted Annuals or any other work. They do a good job, but having grown up working on everything I own, with a Great Depression farmer grandfather who fixed everything rather than throw it out, and a father who does the same...

Not being able to help take inspection covers off, and get down and dirty with the airplane, really peeves me off.

Example: The screws on the airplane are old and some are loose. I'd like to get a nice set of stainless steel replacements and work my way methodically around the aircraft with a mechanic checking behind me later, and just replace them all. I don't think it's unreasonable to do this for anyone with a brain bigger than a grape seed, but to do it here at any of the shops we've used, I'd have to beg really hard, and they'd still say no. Liability.

It may just mean that long, long, term... Building is in my future. But I don't build my cars, and work on those. And I know when I'm out of my league and hire a mechanic on them.

Anyway, still looking for that friendly A&P/IA who works with owners at our airport. I think they keep them somewhere near the Unicorns and Leprechauns. ;-)
 
Tom-D said:
When the FAA sees that the maintenance was completed and no entry was made the owner has a problem, as does the A&P-IA that signed off the last annual.

when the entry was made that entry may be the incriminating evidence that the FAA needs to make its case.

it is just a matter of proving who did what when.
Click to expand...

FAA must pick and chose what they want to go after.
My Cherokee had some major engine issues from a broker and his" licensed mechanic" i.e. 280 hrs smoh, bent crank,worn out of spec cam,lifters, con rods,.
New prop and log book ,no entry as to why replaced. We suspect a prop strike,then poor re assembly of engine and use of parts that barely meet minimum.
Anyway called FSDO ,they said they'll keep an eye on them.
As in another post, the log books are only as good as what's put in them.
I think if/when I buy another plane it will be with a run out engine, then I'll have it done right and know exactly what I have.
 
flyingcheesehead said:
So - Let's say there was a hangar rash incident that crushed a wingtip. [snip]
Sadly, there is WAY too much of this going on out there. :frown2:
Click to expand...

It sounds horrible. People should be more careful with and around their airplanes so these hangar rash incidents don't occur so often.:cryin:
 
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