T-38 Talon… what is this thing?

[bobmig]

While browsing through photos of T-38s something caught my eye. Although the majority of the aircraft have what I would call a “standard” fin/rudder assembly, some have an addition with some kind of antenna or sensor that extends out over the exhaust nozzles. Just what is this thing? And why would it only be added to some aircraft?
Here’s what I refer to as the “standard” configuration.

Here are a couple shots of the addition.

[darthspud]

ECM /Radar fin?

[bobmig]

2 hours ago, darthspud said:

ECM /Radar fin?

That crossed my mind, though it seemed a bit out of place on a trainer.

Bob

[Giorgio N]

That fairing is one of the external features of the AT-38B variant, developed for the Lead-In Fighter Training program in the '70s. Don't know if there's anything inside, will check a couple of books tomorrow 

[exdraken]

hmm interesting!

 

on some F-5s this is where a brake chute is installed.... but I am not aware of T-38s having one.....

 

here is another one:

https://www.bredow-web.de/US_Air_Force/Kampfjets/Northrop_T-38_Talon/Northrop_AT-38B_Heck.jpg

 

seems to be a wedge actually!

http://data3.primeportal.net/hangar/bill_spidle2/at-38b_61-0817/images/at-38b_61-0817_04_of_51.jpg

 

 

[Giorgio N]

Found the answer: it's a ballast "box" used to counterbalance the extra weight that the ventral pylon adds ahead of the centre of gravity. 

[exdraken]

3 hours ago, Giorgio N said:

Found the answer: it's a ballast "box" used to counterbalance the extra weight that the ventral pylon adds ahead of the centre of gravity. 

interesting! Kind of a stabilising function

but would not adding/removing a second pilot or even a full fuel tank affect COG much more, than the pylon ? 🧩

 

[darthspud]

Our Harriers had a very fine CoG. Even pilot changes could alter it more than a half meter forward or back

[Giorgio N]

31 minutes ago, exdraken said:

interesting! Kind of a stabilising function

but would not adding/removing a second pilot or even a full fuel tank affect COG much more, than the pylon ? 🧩

 

 

 

I am not familiar with the flight characteristics of the T-38 family. In general we have to consider that the AT-38 conversion involved adding a number of new parts to the front of the aircraft, including a pylon capable of ejecting loads (and as a consequence in some cases the load itself) and a rudimentary fire control system. It makes sense that something had to be added to the tail to restore the balance.

It should be said that very early pictures of AT-38s do not always show the fairing, so it may be that this was added later in the career of this variant.

[Giorgio N]

Here's a picture from the USAF flight manual for the T38. The items marked with a B beside the description are peculiar to the AT-38B. Notice the mention of the ballast box at the rear and the various items in the cockpit area. The MXU recorder if I understand right was not installed on all aircraft but I'll be happy to be corrected if others know more.

 

 

[Murph]

1 hour ago, exdraken said:

interesting! Kind of a stabilising function

but would not adding/removing a second pilot or even a full fuel tank affect COG much more, than the pylon ? 🧩

 

 

The pylon was used to carry practice bomb dispensers and gun pods, which added to the weight.

 

Regards,

Murph

[bobmig]

Thanks, everyone, for your input. With all your help I now understand what it's all about. Yes... a 'ballast box' as part of the AT-38B modification. Later, when they were upgraded to T-38Cs, the box (empty) was just left as part of the airframe. That's why there are relatively few Cs with the mod.

Bob

[e8n2]

13 hours ago, Giorgio N said:

Here's a picture from the USAF flight manual for the T38. The items marked with a B beside the description are peculiar to the AT-38B. Notice the mention of the ballast box at the rear and the various items in the cockpit area. The MXU recorder if I understand right was not installed on all aircraft but I'll be happy to be corrected if others know more.

 

 

Notice the hand pointing to the B in the drawing.  That means it was a change from the drawing in the previous version of that particular T.O.

Later,

Dave

[alt-92]

On 8/10/2021 at 4:09 PM, exdraken said:

but would not adding/removing a second pilot or even a full fuel tank affect COG much more, than the pylon ? 🧩

If it changes the CoG range beyond what the standard trim settings can compensate for, it's probably wiser to do this.