Su-27 Odd-rod array question...

[geedubelyer]

Hi guys 'n' gals,

I would like some help if possible, please.

Can anyone shed any light on the "Odd-rod" aeriels beneath the nose of the Su-27?

I have noticed that some aircraft have a single group of three antenna, some aircraft have two sets beneath the nose.

Here's what I mean:

(photos by kind permission of Kasatka/

www.aircraftphoto.ru.)

Can anyone offer an explanation for this?

Thanks in advance.

:D

Edited September 3, 2006 by geedubelyer

[janman]

Actually, I've been thinking the same thing as you. Some Flankers in deed seem to have a pair of IIF rods instead of one. I haven't seen any explanation here on ARC, nor anywhere else. Maybe the second set is simply for "reserve"(?)

For my Hase Su-27 "Red 55" I used only one set of rods as the pictures by Linden Hill don't suggest there would be another set of them.

[eye_SPY]

What you are talking about is the SRO-2M Odd Rod IFF system. Here are some odds and ends about this system I was able to find out. (don't ask where)

The baseline Su-27 series, even in Russia, has always used the older "Odd Rods" style antenna rather than the newer blade style antenna. The Su-34 and Su-35 have blade antennas.

The Russian IFF systems remain a bit of a mystery, I'm afraid, but I assume that the SU-27 must have had the newer "Parol" IFF system which was used since the late 70s (the 'Belenko' effect). Perhaps the physical antenna shape (blade/rods) is not related to the actual IFF equipment inside?

Maybe inside the triangle blade is the 3 "Odd Rods" as of old?

The Chinese IFF system is an derivative of the SRO system but not identical, while Indian MKIs use an Indian system.

The Soviet 2S6 Integrated Air Defense System has a defense system which presumably includes an IFF interrogator which interacts with the usual Khrom-Nikel (Odd Rods) IFF system found on Soviet combat aircraft.

The Mi-24V entered production in 1976. Apart from adding AT-6 Spiral ATGM capability, the Hind-E differed from the Hind-D in having TV3-117V engines, revised protective doors for the Raduga-F LLLTV/FLIR, and a larger, non-rotating antenna pod for the radio command guidance system. The SRO-2M 'Odd Rod' IFF was replaced by the SRO-1P transponder, evidenced by the small triangular blade aerial on top the WSO's canopy.

Here they are on a Mig-29:

http://www.b-domke.de/AviationImages/Fulcrum/0629.html Top Location

http://www.b-domke.de/AviationImages/Fulcrum/0651.html Bottom Location

The old SRO-1 systems had the Odd Rods. Newer SRO-2 Khrom-Nikel IFF sets have a small blade antenna.

[David Walker]

What you are talking about is the SRO-2M Odd Rod IFF system. .

I'm pretty sure his question wasn't about the odd rods vs. the blade but why do some aircraft (like the one in his lower picture) have TWO sets of three odd rods right next to each other. Is it a back-up system?

Edited September 5, 2006 by David Walker

[svaz]

Don't most odd-rod equipped planes have one set topside (at the "stinger") and one set down below (below canopy)? I can't tell from these pictures but maybe there was a reason they couldn't put a set up top so they put two on the underside?

[geedubelyer]

Thanks for the help on this one guys. Sergey has posted another explanation in my "in-progress" thread.

Based on the info, I've elected to fit a single set of blades under the nose of my model. Personal preference really and not replicating a specific aircraft (although Bort Red51 is shown having just the one set anyway).