What conditions can cause the TOT to rise during flight and what measures can be taken when that happens?
What’s a TOT?
If I were the pilot, I’d either reduce the throttle or drop the collective. But I’m not a pilot [sub]but I play one on TV[/sub].
Tripler
Can ya elaborate on the original question?
I had to look it up.
Seems that TOT = Turbine Output Temperature.
Aaaah. In that case, I’d say check your oil pressure, and fly faster. Air over radiator is better, no?
Tripler
“Speed is life.” - J. T. Kirk
I don’t know about helicopters specifically but for a turbine engine in general I’d suspect that something is loading up the engine so that more fuel is required to produce the same engine RPMs or there is a change in air density (temperature or pressure) such that more fuel is required to maintain the power output or thrust (for a jet). On the jet I fly it is typically caused by various services that use engine air, such as airframe and engine anti-ice, taking air out of the engine before the combustion section. You get less air going into the combustion chamber and the engine effectively has to work harder (hotter) to get the desired power output or thrust.
We also see it when the ambient air temperatures are high, the engines burn hotter to give the same engine RPM compared to a cooler day. As the engines reach their limiting temperature the available thrust decreases so on a hot day you have less thrust available than on a cold day.
You can also get a similar effect by placing a large electrical load on an engine driven generator. If you’re not careful the load on the engine can be more than it can handle and the engine turbine RPM will decay while the TOT keeps rising. Left unchecked and the engine will fail.
By the way, TOT is just one of a number of different abbreviations for the temperature of the gasses in the region of the combustion chamber. Off the top of my head there is also EGT and TGT meaning exhaust gas temperature and turbine gas temperature respectively. They maybe measured at slightly different places in the engine but the basic concept is the same.
I was expecting to see:
“Need answer ASAP” followed by “Mayday, declaring an emergency” 
If you turn anything extra off but the temperature keeps rising what can you do? Does flying at a lower altitude (denser air) help?
Also another question on helicopters: there’s this gauge with two needles, marked turbine and rotor, like the one right in the middle here: http://helicopterflight.net/intrument_fig_.htm
Which stage of the turbine is this measuring, n1 or n2? Also I read somewhere that the two needles should not split (ie run at different speeds). Why is that?
Any time the helicopter tot acts up, call the helicopter parents.
Edited thread title at request of OP.
Colibri
General Questions Moderator
Does it keep rising until it exceeds the TOT limit or does it stabilise somewhere?
According to the above link that is measuring N2.
I’m not a helicopter pilot so can only give educated guesses until someone like JohnnyLA comes in. In the case of that gauge the green range for N2 is very narrow so you really don’t have any option but to operate with the needles together or with a small split at most. The danger of splitting the needles so that either of them is outside their respective green range would presumably be, in the case of the rotor, if it goes above the red line you would likely get structural failure of the rotor and if it gets too slow and drops below the redline in flight you need more collective to maintain the desired lift which will cause the rotor RPM to continue to decay, TOT to rise, and torque would exceed limits. The N2 exceedences would result in similar consequences, too fast and you risk structural failure of the N2 components, too slow and you risk the engine bogging down (decaying RPM and high TOT.)
There is more information on the website you linked to.
I’ve only flown pistons. Jets are too expensive.
The helicopter rev counter works the same way in a turbine as in a piston helicopter.