I was pretty sure (and was told so) that TVC was tied off FBW during MAKS at least. Regarding LEVCONs – believe me, this is not most weird ‘scissor’ position I’ve seen ’em, but seems that at MAKS this feature was barely used))) Or this was some special day for ’52’

T50-3 has successfully landed. Bogdan (as always) was at the controls
more other good news to come (hopefully) nearest time

http://groomi.livejournal.com/39086.html
T50-3 took off at 4.20 PM local time

I had a few friends doing some outsourced IT work for some folks within HAL Nashik and the stories they would tell me about how things worked there were pretty amazing…

by anishns at BFK:D

http://www.aviaport.ru/news/2009/03/16/168743.html
2 y.o. leak or substitute for real configuration?
picture captioned as taken from Vayu Aerospace and Defence Review

Matinez, Ken –

Finally, answers came:

Paints that we use(d) have bad adgesion with titanium and weathered very fast. As Ti alloys doesnt corrode etc. it was decided not to paint it at all.
Su-34 doesn’t have Ti alloys used in engine nacelles at all as a/c has other flight envelope (in regards of speed range) than Su-27.

quite falls into answer from Boeing guy on F-15 bare metal tail area

The majority of the aft fuse on the F-15 is titanium. Generally speaking there’s no need to paint titanium since it resists corrosion very well. Since I work at McDD (now Boeing) and have worked in F-15 production I can’t speak for LM but I am pretty sure but the aft fuse on the F-16 is aluminum so it needs paint on it for protection.

and this one http://forum.keypublishing.com/showpost.php?p=1043997&postcount=11

The unpainted area is made of titanium, since titanium does not corrode, no corrosion protection, primer and paint is required. There are lots of paints that can withstand the heat but why add weight and complexity when it is not needed, just leave the area bare.

I’m confused, but “Amīcus Plato, sed magis amīca veritas”. Of course, I can invent a theory that paint was weathered fast due to hight T as well, but it would be unfair.

Whatever, that mystery seems to be solved and confirmed by several industry sources.

To solve a discussion, I’ve asked some questions to Sukhoi guys. Hope they will shed light on unpainted areas mystery.
If you remember, initial question was ‘why some areas on Su-27 family engine nacelles left unpainted’ and my answer was because they are hot and suggested that on final T-50 they will be covered with hight T RAM.
It was not a question ‘if Su-34 nacelles painted with temperature-resisting RAM.’ as I remember.
If I was wrong, I will admit it.

Think simple, the engine nacelles of the Su-34 are made from alluminium alloys or a honeycomb structure

I always thought that unpainted areas at engine nacelles are made from titanium alloys (VT-20 and then OT4-1 for Su-27 family, VT23m for T-50). Seems that technical manuals are lying;)

T
The engine bay(space between nacelle and engine) is well vented and cooled by a by-pass flow taken somewhere infront. There should be temperatures no more than 80deg C, therefore saying that engine nacelles are damn hot and need a temperature resisting RAM is simply a BS.

Calculations of the airframe and systems temperature were performed by engineers Gladyshev and Tochilina (she was in charge of the fuel system temperature calculations). As a result “The Index of the temperatures of Object T-10” authored by Vladimir Gladyshev was released as a working document in the early stages of designing the Su-27. It allowed design bureau departments to consider the impact of temperature factors for the choice of materials and strength calculations for the airframe.

Calculations showed that the maximum speed of flight, corresponding to M = 2.35, at an altitude of more than 11 km, airframe skin heats up to 140 – 150 ° C, the temperature of glass windshield reaches 143 ° C, intake duct walls are heated to 175 ° C. In this case, the engine is heated up to 550 ° C in the afterburner area, while in the area of the nozzle feathers – up to 1100 ° C. That required usage of the titanium alloys in the construction of the engine compartment, the installation of heat protection screens on the walls of the tank #4 and the ventilation system to prevent possible explosions in the engine bay in the event of leakage of hydraulic fluid and fuel.

Su-27 Fighter Vol.I: Beginning of Story by Ildar Bedretdinov et al.