T-6 Design Feature Questions

Noha307 · **Posted:** Fri Jun 16, 2023 5:20 pm

A couple questions about the T-6 that I was hoping an expert could answer:

The Flight Handbook for the T-6D includes a sidebar illustration on page 48 that mentions "landing gear downlock lights" and appears to show lights shining out the front of both wings. (The scan is very poor quality, so it is difficult to make out exactly what is being depicted.) Note that this does not refer to landing lights, as they are depicted separately farther up in the same illustration, nor lights in the instrument panel, as they are clearly on the outside of the airplane:
Attachment:

Frustratingly, despite covering the other four types of lights depicted in the illustration, the downlock lights don't seem to be mentioned anywhere in the text. Does anyone know anything more about what this refers to?
According to page 34 of Dan Hagedorn's T-6 book:
Dan Hagedorn wrote:
Although usually described as "BT-9s modified for the USN" in most publications, the Navy described the aircraft this way: "The NJ-1 airplane is a single engine, two-seat, taper-wing monoplane designed for advanced training. The wheels are fixed, but a dummy retractable landing gear control operates landing indicators." [Emphasis Added]

(Source: Dan Hagedorn, North American’s T-6: A Definitive History of the World’s Most Famous Trainer (North Branch, MN: Specialty Press, 2009), 34.)
Does anyone have pictures of this? (I would also settle for pictures of the same type of system in the cockpit of the Fleet Fort if anyone at the Canadian Warplane Heritage Museum is listening. )

Larry Kraus · **Posted:** Fri Jun 16, 2023 7:27 pm

I wasn’t aware of this feature. I was able to find out some information in the T-6G Maintenance Manual.
The first page shows the wiring diagram for the external indicator lights.

IMG_8636 by tanker622001, on Flickr

The next two pages explain that these lights only operate when the navigation lights are on. The first of these pages is for continuity. The second contains the info on the external landing gear position lights.

IMG_8637 by tanker622001, on Flickr

IMG_8638 by tanker622001, on Flickr

The next two pages are from the T-6G Flight Manual. Item 10 on the first page mentions how to check that the lights are operating. The last page is similar to what you posted.

IMG_8639 by tanker622001, on Flickr

IMG_8640 by tanker622001, on Flickr

IMG_8645 by tanker622001, on Flickr

Matt Gunsch · **Posted:** Fri Jun 16, 2023 9:43 pm

The reason for the gear lights on the outside of the center section was so that the controller could see that the gear was down and locked when the plane was on final. If they did not see the lights, they would order a go around and gear check.

Noha307 · **Posted:** Fri Jun 16, 2023 11:31 pm

Awesome! Thank you guys! I should have thought to check the maintenance manual. What a fascinating system as well. As a follow up, does anyone know if there's a T-6 around with this system still installed? I'm curious to see what the lights actually look like and where exactly they are mounted.

Also, my second question about the mock landing gear controls still stands. I am looking to get my hands on a scan of of an early version of the T-6 erection and maintenance manual (for reference, my understanding is that, according to page 4 of the 1944 edition of T.O. 00-1, I think the designation should be T.O. 01-60A-3 through T.O. 01-60D-3) to see if it happens to have a a 3-view line drawing of either a BT-9, BT-14, BC-1 for the aircraft 3-views project, but it might also answer this question too.

Matt Gunsch · **Posted:** Sat Jun 17, 2023 12:09 am

Most T-6s still have the external lights installed, they do come in handy when doing gear swings. They are standard external lights with a frosted lens.

Larry Kraus · **Posted:** Sat Jun 17, 2023 11:15 am

When I was getting my Commercial, multi-engine and instrument ratings through the GI Bill at Santa Barbara Aviation in 1972 part of the instrument training was in a Beech Sundowner. It had fixed landing gear, but had a landing gear switch in it similar to the one in the Baron that was used for multi-engine training. It had a red Up light. I don’t recall if it had three green Down and locked lights it just one. It was useful as a procedures training device for rookie pilots, especially in instrument training with numerous approaches and missed approaches.

Incidentally, you can see the hole where the landing gear extension light is installed just outboard of the retracted main wheel in the picture of the T-6 at the bottom of the last page from the T-6G manual that I posted above.

Noha307 · **Posted:** Sat Jun 17, 2023 2:24 pm

I just so happened to find a good picture of 42-84757 showing one of the lights today:

Attachment:

T-6 Landing Gear Downlock Light.png [ 299.13 KiB | Viewed 8568 times ]

(Source: Warbird Training Center)

JohnB · **Posted:** Sat Jun 17, 2023 9:15 pm

Larry Kraus wrote:

When I was getting my Commercial, multi-engine and instrument ratings through the GI Bill at Santa Barbara Aviation in 1972 part of the instrument training was in a Beech Sundowner. It had fixed landing gear, but had a landing gear switch in it similar to the one in the Baron that was used for multi-engine training. It had a red Up light.

I recall FLYING magazine mentioning that feature at the time.
Back then it was widely believed that a private pilot who trains in a make would stay loyal to the brand as he moved up the general aviation foodchain.
They said something along the line of it will remind a Sundowner pilot that "...there was a Bonanza or Baron in his future."

Another reason may have been to prevent mishaps when Sundowner pilots flew the very, very similar Sierra....basically a Sundowner with retractable gear. I could certainly see a FBO or flying club equipped with both and the potential for mishaps.

Stoney · **Posted:** Sun Jun 18, 2023 9:43 am

you can wire those lights to the cockpit and have gear down lights in both cockpits.

Fearless Tower · **Joined:** Thu May 26, 2011 5:14 pm **Posts:** 368

Matt Gunsch wrote:

The reason for the gear lights on the outside of the center section was so that the controller could see that the gear was down and locked when the plane was on final. If they did not see the lights, they would order a go around and gear check.

I believe you, but seems kind of silly design. Would have been more useful to rig the light bulbs inside the plexiglass gear pin window for the pilot to see at night.

One downside of flying the T6 at night is you have no way of verifying that the pins are in place like you would normally on your prelanding checklist during the day.

bdk · **Joined:** Sun May 02, 2004 1:16 am **Posts:** 11330

Here's mine! One on each side.

Matt Gunsch · **Posted:** Mon Jun 19, 2023 10:13 pm

Fearless Tower wrote:

Matt Gunsch wrote:

The reason for the gear lights on the outside of the center section was so that the controller could see that the gear was down and locked when the plane was on final. If they did not see the lights, they would order a go around and gear check.

I believe you, but seems kind of silly design. Would have been more useful to rig the light bulbs inside the plexiglass gear pin window for the pilot to see at night.

One downside of flying the T6 at night is you have no way of verifying that the pins are in place like you would normally on your prelanding checklist during the day.

it is not there for the pilot, it is there for the poor sap sitting at the end of the runway looking to make sure the gear is down and locked, if he did not see 2 lights, he would fire flares and call for a go around and gear check.

the pilot all ready had gear down and locked lights, and a gear warning horn. In Carl's T-6 we also had gear lights in the rear cockpit, it was always nice to have extra eyes.

Archer · **Joined:** Tue Nov 30, 2004 3:13 pm **Posts:** 446

Fearless Tower wrote:

Would have been more useful to rig the light bulbs inside the plexiglass gear pin window for the pilot to see at night.

But it's the pilots who have created the habit of ignoring clear signals like red lights, the absence of green lights, loud aural signals (gear warning horn) or other types of indication that a gear is not down. Especially in a time where a retractable gear was a novelty, it would have made sense to have an external observer who could save the day (and the costs of refurbishing a T-6 after a belly landing).

JohnB · **Posted:** Wed Jun 21, 2023 12:33 am

Were they on all members of the T-6 family (including foreign sales) or just ac for the USAAC/F and USN?

I ask because a local aircraft does not have them. It spent time in South America where I believe it was sold new.

Certainly, all military air arms would not need such an item if their procedures did not include someone in a tower to warn the pilot if they were not down.I

Also, they could have been omitted in any subsequent rebuildd, unless the FAA were stickers about originality.

So, does anyone know?

Noha307 · **Posted:** Mon Jul 24, 2023 5:23 pm

A third question:

According to page 128 of Dan Hagedorn's T-6 book:
Dan Hagedorn wrote:
There was one additional development of the late AT-6F series. This involved 44-81661, which was assigned for duty as a crosswind landing gear installation test aircraft around 1 December 1950, and it received the designation ET-6F.

(Source: Dan Hagedorn, North American’s T-6: A Definitive History of the World’s Most Famous Trainer (North Branch, MN: Specialty Press, 2009), 128.)

An article by Carol Glines offers additional detail by stating that had "swivel" landing gear.

Does anyone have any more information or pictures about this aircraft? I am quite curious what this could possibly refer to and how an aircraft with such a feature - at least as I can best conceive of it - would actually work.

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T-6 Design Feature Questions

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