Can someone clarify some details about aircraft mods/ammendments for me?

doesnt RTP mean reduce to produce, ie return all spares still usable

Please do sent it over (you still have my email address?)

I don’t think so; having had my mailbox hacked, last year, I tend to delete “finished” messages, to ensure it doesn’t happen again. This may seem a little over the top, but one of the spam messages was received by the widow of a man who’d died from cancer three months earlier.

Actually what L.T.C and R.T.P stood for was my next question. The first 11 mods for this aircraft are all based on L.T.C minutes (and all class 2) so my assumption is they are pre-production modifications when the aircraft was still in the early prototype stage.

I’ve only really researched the Spitfire, but a class 2 mod could appear at any time (Spitfire mod 1013 “to strengthen engine mounting” was introduced on the Mk.V [due to the Merlin “M” type] as late as August 1944.) R.T.P. is an unknown, but “P” often meant “parts” or “party.”

But just to clarify some of the opinions presented – would the appearance of the Mod in the aircraft’s technical Air Publication indicate it’s actually being seen “in the wild” or is it a simple a notice to riggers that “you may come across this”. Is the date in the index cards where “Approval has been given” the actual notification that this modification is being put into place on all aircraft with the indicated priority class?

A listing, in the A.P., was just a flag, to indicate to the groundcrew, M.U. personnel, or whoever, that the mod existed, with the classification to tell them of its importance. Usually, there were mod plates, somewhere on the airframe, with the numbers stamped on them, so that the crews could assess what needed their attention. Index cards are out of my research “zone” (meaning I’ve never heard of them,) so I don’t want to hazard a guess as to their role.

Edgar,

Please do sent it over (you still have my email address?) I was at the TNA last week and didn’t get half the documents I needed in the end so this might help unravel the mystery. Actually what L.T.C and R.T.P stood for was my next question. The first 11 mods for this aircraft are all based on L.T.C minutes (and all class 2) so my assumption is they are pre-production modifications when the aircraft was still in the early prototype stage.

But just to clarify some of the opinions presented – would the appearance of the Mod in the aircraft’s technical Air Publication indicate it’s actually being seen “in the wild” or is it a simple a notice to riggers that “you may come across this”. Is the date in the index cards where “Approval has been given” the actual notification that this modification is being put into place on all aircraft with the indicated priority class?

During the war, there were 4 basic mod states, of which no.1 was the most important, in fact a Class 1 mod meant immediate incorporation, and all aircraft grounded until it happened. Class 2 was a step down from that, but also had to be incorporated on the production line.
Modifications had to go through a strict process, being notified to the Resident Technical Officer, who had to get the approval of the Local Technical Committee, before any went ahead. There’s a 19-page report, on how the system worked, in the National Archives, which is far too big to put on here, but, if anyone would like a copy, I have it on computer.

Is it possible that the mods that require higher numbered mods before they can be performed (e.g. your example of mod 51 requires mod 138 to have been done first) were larger scope mods that took longer to develop, and by the time they’d made it through the design process, other mods had been developed that affected how something needed to be performed. An example might be replacing fabric wings with metal wings would take some time to develop, and if the number was assigned at the inception of the project, it’s easy to imagine that many small mods could be produced during the development process of the large mod. If one of those small mods affected the way the metal wings were to be fitted (e.g. something changes with the aileron rigging), then you’d need that “later” mod to be embodied first.

Mod’s

And there’s me thinking the Mods were there to keep an eye on us Forumites!:D

Anon.

As said a minefield, not all mods may be embodied or even needed, hence the weird way they come out, As an example of what I mean…. say a Mod comes out for the installation of Radio set and that is MOD 22, the aircraft may not need that particular radio fit due to its operational area, however Mods would continue to be issued for that aircraft, which is then up to MOD 32, the aircraft may the change theater and would then be brought up to the standard for a particular theater which requires MOD 22 to be installed.. As a classic example in the news, think of the bomb dropping Mods for the Dambusters which was removed later, say in theory later in the war it was required again, aircraft would need to be modified again and that MOD number would precede those that came after. You would also have mods referring to different engine types such as a radial engine Lanc that would not be needed on the Merlin version.

Getting back to the Civi world I have several aircraft that haven’t had strengthening Mods embodied, because they are only required if any signs of cracking is detected, as the aircraft do really low hours it was decided to leave them by the owner and do the enhanced inspection regime as mentioned in the Mods as an alternate.

mods are abit of a minefield even on modern mil a/c, let alone what the pace of experience and technology was back then to a ‘standard’ a/c,mod classes do depend on how fast they should be embodied with regard to safety or operational requirement, a lot of mods could be manufacturer only or even ‘WOTSAC’ ( when old type stores are consumed). the suffix may relate to fixed fitting, i.e part A is fitted as part of the a/c fit and part B is role or theatre fit.