September 23, 2020 VOLUME XXXVIII
Welcome to Fall, Grumman World.
Next month we are having three events.
- Formation Flying
- Strip Festival
- National Gathering
We have also added a new hotel to the growing list thank to a pilot in Florida who is attending. Thank you for the info and the discount.
It is very important for us to get our headcount for the event. Go here to register:
We have folks coming we know from the East coast, Oregon, and Florida. Maybe get a few local planes as well. We do have a fun time planned for all. Plan a group flight with you local Grumman pilots and enthusiasts. Thanks to Jeff Johnson for the Facebook posts about the upcoming event on our Facebook page.
BTW, many of the planes seen in our videos will be in attendance and you can ask the owners all about their work. May be a seminar or two in this. Also, video seminar is being worked on.
Also want to thank Ned Thomas for stepping up as an additional Facebook admin for the GPA. Thanks Ned.
On the FF event page there is video showing Whizz and Walkman back in the day of FF at the Cathouse.
Walkman is proposing a dinner Wednesday night for a briefing so that Thursday you can fly when fresh from rest. Stay tuned for more on that.
To further entice folks, I am running some deals and did I mention that we have Door Prizes? For deals we have some oil on sale and air box vents for the front.
We hope to see you there. There will be one big hangar party most likely Saturday in the new big hangar. There is even talk of a party at Roscoe and Luann for some face time.
Prop Bolt Torquing on Tigers
Here is what Ken Blackman had to say many years ago on the Grumman Gang about the Prop Bolt Torquing on Tigers, especially.
Hi Gang, (especially Tiger and Super Cheetah owners),
> Following the threads on this subject, I want to clarify some things so
> everyone is on the same page. First, the reason we have the problem is
> twofold. The original spinners on the Tigers and Cheetahs had the backplate
> sandwiched between the propeller hub and the spacer. These (especially
> Tigers) were cracking like they were made of glass, in the late 70s, so the
> Grumman Engineers went to work to develop a fix in the form of (first) a
> similar unit to the old AA-1 series, which had a fixed aluminum forward
> bulkhead riveted into the dome. It still cracked. The next-gen was what we
> have now (SK143-1 & -2) which took some time to get certified. (There was a
> service letter available from Grumman that allowed the planes to fly with
> the entire spinner and aft bulkhead removed until the new design spinner
> system was available.
> There was an unexpected problem with installing the new spinners in that the
> McCauley prop bolts were barely long enough to be legal with the original
> spinners. The new aft bulkhead was twice the thickness of the original plus
> the forward bulkhead and its required steel doubler were added for a total
> additional 0.123 (to 0.128 with a TCB composite front bulkhead) of
> bulkhead material what subtracts from the available thread penetration of
> the prop. bolts. Thats an eighth of an inch! For this reason the SK-143
> kit instructions said to omit the washers under the bolt heads which caused
> serious damage to the metal of that steel doubler. Thats all for the first
> part of the twofold problem. The 2nd part was that the propeller drive
> bushings (the things pressed into the crankshaft flange) were specified at
> Lycoming (by some dummy) to be of the length normally found in engines that
> would get a constant speed prop installed on it. Two of them are shorter
> than the other four. When the starter ring gear support assy. is installed
> there is none of the shorter two protruding through the front of the support
> and only a tiny bit of the other four. When the backplate is placed over
> these they barely peek through the holes enough to get the propeller
> spacers counter bores to have anything to slide over. Now someone has to
> start the prop bolts into the drive bushing threads and run them in until
> they contact the forward bulkhead doubler and draw it snug to the propeller.
> What happens to cause the punch out of the bulkhead is it tends to slip off
> of the drive bushings and rest on the prop bolts. When it is torqued down,
> the leading edge of the bushings and the counter bores of the prop spacer
> acct as a die and receiver punch that clips out a crescent shaped piece of
> the bulkhead at each of the 4 protruding bushings. (This will cause the
> holes in the spinner not to align with all the ones in the aft and forward
> bulkheads and should stop any mechanic who is awake from continuing and
> start looking for a problem. We see some spinners with elongated holes that
> were filed out to force it to allow all the screws to be installed. Of
> course the back of the spinner will wobble.)
> NOW, try to picture all this going on with one person doing the job. The
> maintenance manual revision, which covered the new spinner system (that was
> standard on about the last 320 or so Tigers in 1979) suggested taping the
> aft bulkhead to the nose cowl to hold it in place while the prop was
> installed. This does kind of work but still two people doing the
> installation is much better though still not foolproof.
> When I did the first installation of the Sensenich 76EM8S10-0-(pitch)
> propellers, on the 180 HP Cheetah conversion development, Sensenich did not
> have the right length bolts since they had never built the dash 10 spacer
> version of the 76EM8 prop. We had to use McCauley bolts until them got them
> made and certified. They designed the new bolts < inch longer than the
> McCauley bolts which allowed using the washers and still getting adequate
> penetration through the drive bushing threads. This was in early 1981 and
> the problem of punched out aft bulkheads had not yet become a wide spread
> problem. Soon after the STC was issued for converting Cheetahs to 180 HP,
> Ameromod Corp. was awarded STC SA1195NW approving the installation of the
> same series of Sensenich propellers on AA-5B aircraft. When the punched
> bulkhead thing did become noticed as a more common a problem, nothing was
> done about it in form of even a service letter, let alone any attempt to
> correct the root source.
> In late 1985, after the split of Ameromod Corporation and we formed Air Mods
> N.W., I certified the 2nd STC for installing the Sensenich propellers on
> Tigers. Part of this new STC covered a fix for the bulkhead syndrome by
> authorizing the replacement of the two shortest drive bushings with much
> longer ones (from the O-360-A4M model engine) OR replacing all 6 of them.
> The Cheetahs and Travelers never had the problem due to longer drive
> bushings which held the aft bulkhead in place during installation. This
> offered the same effect on the Tiger when the bushings were replaced.
> Another fix STC SA3326NM offered is a much more detailed installation
> instruction for putting the propeller on without damaging the bulkhead. It
> also covers what can be considered for the airworthiness of a damaged
> bulkhead. If there are still two undamaged holes in it, it can be used with
> the longer drive bushings or possibly indexed differently than recommended
> in the maintenance manual. (This can help offset the cost of the two drive
> bushings if you choose to replace them. they cost around 500 bucks for the
> The bottom line of all this verbiage is that there is a way to eliminate the
> problem of installation damage. As for the statement made by Dave Fletcher
> regarding the requirement of checking the torque of the bolts at annual. He
> is absolutely correct. However, removing the prop does create the risk of
> damaging the bulkhead on reinstallation. If you know it was not damaged
> before, and the prop was correctly installed, I would not recommend doing
> more than to break the torque, back out the bolts far enough to inspect the
> front bulkhead for cracks, and re-tighten the bolts. If you do not know,
> and cannot verify, the correctness of the installation it is a good idea to
> pull the prop and inspect the aft bulkhead. If the bolts are installed
> without the washers, you should add them. I use an MS27183-18 washer
> instead of the AN960-8 which has a greater outside diameter and spreads the
> pressure of the highly torqued. bolt causing less damage to the doubler
> and forward bulkhead lessening the tendency for the bulkhead to crack around
> the outside of the print of the washer.
> OK, that is your lesson in Grummanology from The GURU for today. If
> anyone wants to discuss it with me, please call me or e-mail direct.
> Ken Blackman
> Air Mods N.W.
Thanks Ned for posting this! It sure is nice that some of this
knowledge (Ken’s) has been preserved.
I’ve been working on Grummans (primarily Tigers) for 33 years now and
had never read Blackman’s comments above before. I suggest everyone
read this and understand the importance of it and how important the
installation of the propeller is! I have worked on numerous Tigers that
had the holes in the aft bulkhead (spinner back plate) punched out from
an unsuspecting mechanic. I will admit that I did it myself when I
first installed a prop by myself. I realized something was wrong when
the bolts didn’t tighten down as they should, but just kept turning and
turning as the crescent shaped pieces were being punched out! Since
then I have installed props by myself and it is NOT EASY. It can be
done but it is much better to have some help.
I wholeheartedly agree with Ken’s last paragraph and I would suggest
that owners print out this paragraph and the pertinent part of the
second paragraph and keep it in the plane and in the log books where any
mechanic who removes the propeller or does an annual inspection can
refer to it. After all it has to be done every time the alternator
and/or belt need to be replaced with the stock nose bowl. I wouldn’t
let any mechanic R&R the prop on a Tiger I owned without understanding
how critical the installation of the spinner and bulkheads are.
———————– END OF Grumman Gang Post ——————————-
Anniversary Video Solved
As many of your know, we were preparing for August 24th which was the fourth anniversary of our first video on Grumman Pilots YouTube channel. This goal met with a few complications.
I had most of the video in the can and was waiting to film a few face on shots and add a few voiceovers and labels to the video in the editor. I did the face on shots one day but the audio was too high via mike placement. Finally finished it (or so I thought) and put it on YouTube. It was immediately flagged as copyright infringement due to me including the 10 second clip of our first video which has audio playing a CELINE DION SONG. Now the original video is not flagged, go figure. So I deleted it on YouTube and edited out the 10 seconds of audio and put it back on the channel.
Then as I always do, I watch it on YouTube and follow along in the editor, checking off the script notes (11 pages for this video) and basically QA it. Oops, had section of video missing from the final cut but still in the editor. So delete this copy and back to the editor.
So finally it is done, It goes on the channel, and I watch some of it, send out a GG message about it. Then I get a call from Shop Monkey telling me what is wrong with the video. I go and watch all of it, and he was right. The audio was all over, low in many spaces so you could not understand it, and too loud in others. Rubbish, so I delete it. My bad.
So in starting over again from scratch, I began putting the video together and found out something that I had forgotten. I had a YouTube VIdeo account from 2011 where I could put videos (and folks could find them and watch no ads -not monetized) and I found a few videos I had done back in 2011 including a Grumman Fuel Leak Find that Jimmy Candeletti and I did in my garage on a very cold winters day. That was 5 years prior to my channel videos.
The Fuel tank video was put on the channel with some editing the other day.
Check out YouTube by searching for Roscoe1024 and you will find them. It included a cherry pie video that Luann and I did one night about 1 am using a new pie stencil cutter. Then the shop at Yankee Aviation got busy and the sawmill took off as well. Busy time. So video went on the back burner yet I kept taking stills. That is where that big photo collection on the website comes from in all the forum post over the years.
So I am finishing up the ‘Anniversary Video’ and it has a few new things in it. Let me say this, after 5 days of no sleep in the ICU, I got out, went to the airport to check a plane in for maintenance. Found a bad starter front baffle seal, so I remade it, and installed it. Then went home, made a video of it, had some food and went to bed. I was so wound up from those 5 days, I had to do something. Here it is:
I also put out a video that I got from Goldpilot in C about the art deco sculpture. Inspired a new Gathering Game. Stay tuned for that! During the events coming up, you can select a part from my huge inventory of Grumman parts and figure how to retask it into something else. Maybe a horizontal stab into a book shelf? Stay tuned for that during the upcoming events next month.
Also let me say that I have a few extra camera and mounts for them in and out of an aircraft for video gathering during the events. FYI
So to close this tale, anniversary video is almost finished but needs a few more bits. One of these is thanks to Mark Matthews, i.e. Trash Pandas (more to come)!
Interior Redo Video
Thanks to Tim and the fine job he is doing maintaining Spanky a beautiful 1969 Yankee.
As Tim says, it was a ton of work that I will never do again. The basic comment on video viewers is that Tim just added a bunch of work to their restoration. The funny part is that for all this work under the covers so to speak, no ones but you will ever see it. But you know it is there and done right.
So in closing, enjoy Fall, the WX here is great. Now I am off to plan more event stuff.