Gyro Gunsights

Greyman said:

Yes the initial GGS design that made it to service was the Mk.IIc which was meant for gun turrets, the Mk.IId was the fighter sight. In USN service the Mk.IIc was the Mk.18 and the Mk.IIc was the Mk.21. After initial low enthusiasm the USAAF eventually came on board and adopted the Mk.IId/Mk.21 as the K-14.

I think the added functionality for rockets came from Ferranti. In May 1945 the Director of Armament Development in the UK sent over (among other GGS technical data) drawings for Mod.19 FE to the US. This Mod introduced the RP attachment and raised the sight to 'Mk.IId Series 2'. For what it's worth the new orientation of the graticule called for by Mod.19 was also introduced to the current Mk.IId Series 1 production, in case retrospective fitment of the RP attachment was called for.

EDIT: I also note the first photo you have there also has Mod.20 FE; which introduced the sliding sunscreen and brought the sight to 'Mk.IId Series 3'. Drawings for this were also supplied to the USA in May 1945.

Click to expand...

I believe that in1945 the P51s in Iwo Jima were already using the K14 (I saw them using it in a ground strafing gun camera film, after scorting the B29s).
About the RP in the MK IV Ferranti, it had a fixed deflection of about 17 mil (that is what I can still remember) and it was not adequate for the HVAR that we used. But we found that we could deflect the + on the the fixed recticle by turning a smal spring knob on the back of the sight and in this way could place the + in any deflection we needed (by using the gyro recticle as reference) , and thus, used the fixed recticle for aiming. After use, all we had to do was to level the + it with the piper on the gyro recticle (provided we were in absolute undisturbed level flight) for using with the guns. We prefered using the fixed recticle for strafing and used the gyro only for air to air gunnery.

I'm not sure when the K-14 first started being used operationally by the USAAF, but it was March 1944 at the latest. As with most other pieces of equipment there were many variations/modifications to the K-14 throughout its service life. So just like a Mk.IId, a K-14 in February 1946 could have quite a few differences with a K-14 in 1944.

Basically what I'm trying to say is that a mid-44 K-14 used by the 8th Air Force wouldn't look like the one in the photo.

Do you know if all of the early US sights were produced at Bendix? I found this interesting bit:

At a conference in Washington last Tuesday, General Childlaw, Major Elliott and myself conferred with a delegation from the Navy regarding the possibility of the Army obtaining some Mark 18 sights from the Navy for conversion for fighter use. General Childlaw stated the case so well that the Navy reversed its former decision and we are now to get a major part of the present Navy production. The production bottleneck at Bendix has been broken and sights are now being produced in quantity. I am visiting the Eastman plant at Rochester tomorrow with a Naval officer from Washington and we will get the Eastman production line changed from the turret sights to fighter sights. It is expected that enough sights will be obtained to equip all of the P-51's and part of the P-47's in the European theater of operations. As soon as the first two sights are produced I am taking one of them out to the North American Plant at Inglewood so that they can engineer a kit which will be suitable for field installation. If everything goes well, some sights should be delivered in ETO within two months.

...

The first sights which will be sent to the ETO will be "quick and dirty" modifications of the Navy sight. The gravity drop correction will not be used and no super elevation of the moving reticles will be made. A cleaned-up version will appear in about three months.


This was in a letter to a Colonel H.G. Bunker from a Captain N. R. Peterson, 7 February 1944.

I wish I could have heard what General Chidlaw said!

Greyman said:

I'm not sure when the K-14 first started being used operationally by the USAAF, but it was March 1944 at the latest. As with most other pieces of equipment there were many variations/modifications to the K-14 throughout its service life. So just like a Mk.IId, a K-14 in February 1946 could have quite a few differences with a K-14 in 1944.

Basically what I'm trying to say is that a mid-44 K-14 used by the 8th Air Force wouldn't look like the one in the photo.

Do you know if all of the early US sights were produced at Bendix? I found this interesting bit:

At a conference in Washington last Tuesday, General Childlaw, Major Elliott and myself conferred with a delegation from the Navy regarding the possibility of the Army obtaining some Mark 18 sights from the Navy for conversion for fighter use. General Childlaw stated the case so well that the Navy reversed its former decision and we are now to get a major part of the present Navy production. The production bottleneck at Bendix has been broken and sights are now being produced in quantity. I am visiting the Eastman plant at Rochester tomorrow with a Naval officer from Washington and we will get the Eastman production line changed from the turret sights to fighter sights. It is expected that enough sights will be obtained to equip all of the P-51's and part of the P-47's in the European theater of operations. As soon as the first two sights are produced I am taking one of them out to the North American Plant at Inglewood so that they can engineer a kit which will be suitable for field installation. If everything goes well, some sights should be delivered in ETO within two months.

...

The first sights which will be sent to the ETO will be "quick and dirty" modifications of the Navy sight. The gravity drop correction will not be used and no super elevation of the moving reticles will be made. A cleaned-up version will appear in about three months.


This was in a letter to a Colonel H.G. Bunker from a Captain N. R. Peterson, 7 February 1944.

I wish I could have heard what General Chidlaw said!

Click to expand...

I really do not have the profound knowledge of the technical and historical aspects of the evolution of these gyro sights that you have. I'm learning with you.
One thing I had always questioned is where the Navy planned the use of the Mk 18 turret sights (this is also confusing because they had a MK 18 sight and a Mk18 system which comprised the whole turret components). I never read about the Naval Liberator ever needing defensive armament since their job was to sink UBoats.
Maybe they had planned using them on the Privateer and post war PB aircraft.
Very interesting to know that they thought of converting the MK18s for fighter use. It is one doubt I had, if the Hellcats, Corsairs and Bearcats ever had the K14 installed on them. I know that some P47s had them in the ETO but not in Italy where the ones operated by the Brazilian AF, and also the american ones of the 350 FG, still had the MK8 fixed recticle, also a heritage from the british Mk II (?) or something else used by the RAF (I find it very confusing the names of the english sights). In the collection I had, there were the odd MK 9, 10, 11 and 13 specially projected for usse in specific turrets (tail, waist, top and nose) of the american bombers and not position interchangeables. They had the pursuit curve of the atacker programed in such a way that the sight aimed at the atacker while the guns were pointig to where they should hit the target. I do not know if they were used operationally. And there was also a huge K4 that I simply gave away so large it was.

Yeah the fact that the company name and the service name get thrown around tends to confuse things.

Barr & Stroud GM2
Pilot's Reflector Gunsight Mk.II
(American Mark 8 sight based on this)

Barr & Stroud GJ3
Free Gun Reflector Sight Mk.III
(American Mark 9 sight based on this)

Zipper730 said:

Aren't star-tracking systems also complicated,

Click to expand...

Replying to a necro-thread here, but Google sent me here so...

Star trackers are very simple. They're basically a spinning disk in front of a light sensor. The disk contains a series of radial slots cut in it. When the slot aligns with the star there is a brief flash of light on the sensor.

The disk is being spun by a synchronous AC motor. When a flash is seen, the angle of the star relative to the seeker is represented by the phase of the signal.

And that's it. It's pretty much identical to early IR missiles with the practical exception that the telescope in front of the reticle is much more powerful, and that one has to have some external reference, typically an inertial platform, to provide the initial aiming during setup.

Zipper730 said:

I understand that they use a gyro to sense the movement of the aircraft, but what I'm uncertain about is how they avoid tumbling the site during aggressive maneuvers...

Click to expand...

The gyro is not in gimbals but rather is a "rate gyro". That's to say it only moves a small amount. See the patent drawings at: Navy Mk. 18 Gun Sight

XBe02Drvr said:

Is there anything aeronautical (or nautical) that the Brits didn't think of first?
I read recently that the Philadelphia shipwright whose diagonal bracing made the Constitution class frigates so hard to sink in the war of 1812 actually pirated the idea from the Brits. They hadn't successfully used it in their own ships because they didn't have the right wood (live oak) to make it work properly.
Cheers,
Wes

Click to expand...

yes - dynamically tuned mechanical gyros, roll on bearings, gull wings, jet engine, infrared detectors, flush rivets, nuclear propulsion, comprehensive unit system (metric), missiles, gunpowder, magnetic compass and many, many others. But definitely UK holds one of most notable places in technological civilization development.