Supertweet

N87921 is almost ready for flight testing.  It’s taking some more time than expected for many reasons. But not for a blog.

It’s time for taxi testing at high speeds but the radios were not working properly.  Poor transmission and the intercom went kaput.  We pulled the system apart and found the wiring under the co-pilot’s intercom panel bad.  We rewired the system, including new microphone cord.  Thought it is working well, then it went tango-uniform again.  We think we have a bad antenna wire (new) and will pull out old stuff.

I’m anxious now to get this bird in the air.  I’ve missed too many fly-ins and Jet Blasts.  Will let you all know this weekend if I get it fixed.  If so, expect a follow-up on high speed taxi tests and radio work.

Still must do high power run ups and see if my governors are working correctly. Impossible to tell right now without burning up the asphalt.

Stay tuned.  More to come.

Which is best?  One really better than the other?  Both feel the same, look the same.  5606 cost significantly less.  So why use 83282?

My observation:  5606 works fine.  It does, however, gum up and get tacky, sticky.  Especially when not used a lot.  For aircraft that are operated very regularly, I’d say 5606 is fine.  But don’t leave it for extended periods in your lines and cylinders.  Hydraulics seem to bust O rings more often and the wipers don’t work smoothly.

Using 83282 is about 3 times more expensive.  It remains fluid, maintains its viscosity.  It does NOT get sticky.  In fact, if there is a minor O ring leak, the 83282 will find it more readily than 5606.  And the leak will NOT slow down or stop as it does with 5606.  For those of us who fly only a few hours a year in their warbirds, I’d say 83282 is the way to go.

With hydraulics, you’ll need to have access to a good hydraulic mule.  I finally purchased one with variable pressure and flow.  Now I don’t have to borrow one when needed.  In fact, I find myself using it a lot more for systems checks and not using petro-dollars to do it.

The other pilot who has worked with me on the project has been doing a non-scientific test for several years on the two fluids.  The observations are interesting.  He put in equal amounts of each fluid in glass jars and inserted a pencil and a piece of aluminum tubing in each jar.  After 2 years, the 5606 was getting thick by a large degree.  Now, after several years, the 5606 is like peanut butter.  The 83282 looks as fresh as the day it was poured.  It flows easily. 

I’m sticking with the 83282.

921’s windshields and canopy had deteriorated beyond salvage.  Because there are no replacements available, I decided to have new bird resistant polycarbonate panels made.  I turned to L.P. Aero Plastics to do the job.  We worked closely together for a LONG period of time to make sure we got it right the first time.

We realized the original shields were too weak and wanted to increase the thickness for added protection.  This would cause MAJOR problems because it would change the alignment of the canopy height relative to the surrounding sheet metal of the fuselage.  And the original way in which the glass was installed could not be realistically reproduced. Besides, I don’t feel it was a very good installation anyway.  So a plan was drawn up and given to LP Aero.  The entire canopy and windshield frame was boxed up and sent to them as a form.

I designed a routed inside edge to the windshields; 1/4″ outside lip, 1/4″ inset of frame. This would force modifications to interior components.  But it would work if we were careful.  We were careful.  The new completed windshields are optically perfect and fit correctly.  They can be replaced more easily than the originals.  Note:  The glass panels themselves are NOT drilled.

Included are close-ups of the canopy mods we made with the assorted pieces.  They include, from inside to out:  spacer, gasket retainer, strips of gasket material, Teflon tape, the canopy glass, Teflon tape, gasket material,glass retainer strips of aluminum, an edge guide of 1/4″  x 1/2″ aluminum bar stock.  Then final cover by the fairing.  All match drilled.  The bar stock was difficult to fabricate as it followed the compound curve of the canopy frame, had to stay FLAT on frame, and was match drilled to the canopy and countersunk.

This  sounds easy, but was fraught with misalignment issues.  The barstock had to be torqued into position to its final set position AND exact height before it could be drilled 90 degrees from the canopy frame.  (The height issue must be consider because the spacing of bolt holes at the frame is different on the bar stock.  The bar stock holes that sits 3/16″ outside the of the frame are further apart.  Consider it is following a slightly larger circumference of a circle).   A canopy jig would have made the difference, but needless to say one is not available.  When the bar stock issue was finally completed, we made another set in case another aircraft needed to be modified with new panels.

The complete canopy was loosely assembled and put into an outside storage container that heated up during the day in the hot sun (temp would rise to 150 degrees inside!).  When the box was warm, we tightened the screws down to slowly pull the glass into its final resting place without stress.  The canopy baked for two weeks as we alternately loosened then tightened the holding screws. There appears to be no excess stress points on the glass and is allowed to “float”.

In any restoration, there comes a specific item in the process that holds a particular special place in your heart and memory.  The canopy and windshield are these “special places” for me as I was told that there were no replacements and the system could not be duplicated.  Having not done this type of restoration before, it gave me pause to consider the incredible work done by others who do this for a living.  I’m proud of our final result and don’t mind sharing it.

921, after being abandoned for over 30 years, acquired an assortment of dings, dents, stolen equipment, and other assorted insults.  But it was complete, airframe wise, and with its old engines in place.  It was boxed up a second time and sent via ship to the US and its new home to be refurbished, restored, rebuilt, to new standards.

Every system, component, hose, hardware, cylinder, seal, was removed and made new again.  Every hydraulic cylinder was found to be corroded beyond airworthiness, so new ones were fabricated, including shafts, wipers, O rings.  Metal sheeting was replaced on the fuselage and tail where damage had occured.  All controls, originally magnesium, were replaced with aluminum, then painted and re-balanced.

The panel was kept as original as possible, all instruments overhauled.  All wiring was either replaced, removed, or re-tested to ensure proper functionality.  The explosive devises in the aircraft, the ejection seat charges and the canopy explosive shell, were removed for safety purposes.  The jettison capability for its armament was removed and all underwing pylons were made to be fixed in place once attached.  External fuel tanks can be removed by conventional means by putting a holding cradle underneath the tank and activating the internal manual release lever in the pylon.

The engines were replaced with two new overhauled J85-17A engines, zero timed, with all new or overhauled accessories.  Capable of 2,850 pounds of static thrust each–5,700 lbs total, the A37B has no problem pushing an empty weight of 5,572 lbs.  The starters were overhauled and have proven to be more than capable of spinning up the little General Electric fuel burners.

This is the story of how a Viet Nam warbird was born, went to war, abandoned, then recovered from a salvage yard, to be restored to flight status again.  The little fighter-bomber will fly again as a tribute to those who have  answered the call to arms, and paid a dear price.  We should never forget our brothers in uniform.

Here begins how one aircraft, Cessna #68-7921 Dragonfly, known as the “Supertweet” by most, will fly again through its discovery, collection, and long restoration.  This, like most “warbirds” are owned and restored in private hands, with our own funds.  Done for the love of aviation and military history.  Call sign “Dragon 921”, looks fresh from the factory. Except for the bullet holes.

Note:  “Owners” of warbirds is a misnomer.  For we may have title, but we are in fact only custodians of historic relics.  To be passed on to later generations for them to keep alive and flying.  These are pages of our history.

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Leaving it’s hardened hanger in Da Nang, Vietnam in 1972, 68-7921 taxis out slowly for another close-air ground support mission.  Developed from the Cessna trainer, the T-37, the greatly upgraded A-37 (”A” for attack) quickly turned itself into a fierce little warrior in the air over Vietnam.

Its greatest strengths were its bomb load carrying capability coupled with its pinpoint accuracy.  One FAC (Forward Air Controller) directing a mission  yelled over the radio when the F-4s were replaced by A-37s; “Thank God!  Now I have somebody who can actually hit the damn target!”.  With two engines, it could loiter for extended periods by shutting down one engine and circling high above the ground fire.

68-7921 is restored to its original condition and will be exhibited in the US as a flying museum in honor to those who flew this wonderful aircraft.  Particularly, this aircraft will honor the memory of Lt. Michael Blassie, USAF, who was killed in action in Vietnam in 1972.  See the story of Lt. Blassie in the “Links” section.

68-7921 will fly to honor its role in Vietnam.  It is a rare aircraft, indeed, with only a handful flying today.  It is small, quick, it is loud.  It’s restoration was, and is, a long one.

The picture above is 68-7921 in flight during the Viet Nam war – Flown by the South Viet Nam Air Force.