FAIL on ITT scale - CJ1+/CJ2+

[Cecco]

On powering up our aircraft Citation CJ1+/CJ2+, due to the current arctic cold, both sides of the ITT scale showed FAIL. With the GPU connected, it took 15 minutes until the avionics indications were sufficiently warmed up and the FAIL indications disappeared. Of course, I wouldn't try to start an engine with the ITT temperature scale missing.

However, I was wondering if the FADEC would block an engine start due to that information missing (No eng ctrl sys fault was on the annunciator panel!) Due to the fact, that the ITT temperature scale is merely indicative with fixed temperature limits (as opposed to N1 limits set by FADEC depending on OAT etc.) and the pilot being responsible for aborting an engine start, I suppose, an engine starst could be made. What do you think?

Cecco

[sycamore]

Suggest you check your insurance first.....

[frontlefthamster]

With respect, insurance has nothing to do with it. This is down to flight crew and perhaps their engineers.

If operating privately, you have no option but to warm the aircraft up with available resources and hope it works...

If operating commercially: Prior to despatch, consult the MEL. If it allows you to operate without ITT indication, you may continue (though I would still speak to engineers). After despatch, consult the QRH or equivalent.

Either way, balance your own thoughts about flying a very fun little jet with the fact that it's not a robust aircraft, and just isn't up to a lot of the jobs asked of it. Cold weather starts are one of them.

...oh, and always check by hand that the N1 stage rotates properly prior to start in low temperatures or after a significant period parked, or you will be in deep and costly poo. It's OK to walk on the inboard sections of the wing to access the fan - see the manuals for details, but basically the structure under the 'walkway' on the RHS is mirrored but not marked on the LHS.

Whilst having a typically Septic 'guarding the six' appproach, the Cessna support folk are usually quite competent and helpful, as long as you're not pointing out some of the weaknesses of their designs or manuals.

[flugzeug]

We also operate a C525, and it happened a couple of times to us. Once we warmed up the engines applying hot air into the inlet. After 5 min on each engine, the "FAIL" on the ITT scale dissapeared. Another time we tried to start the engine with the ITT Fail indication, with the intention to abort the start if the indication wouldnt become normal (we go to Throtles iddle at 8-10% N2). The moment we pushed Start, the indication became normal.

I am not sure what the MEL says, but for sure one can not fly without ITT Temp Indication, but IMHO to try to start the engines can not do any harm.

Kind regards,

[His dudeness]

but for sure one can not fly without ITT Temp Indication, but IMHO to try to start the engines can not do any harm.

Maybe I´m wrong, but IMO the ITT is the most critical thing on starting...

I would not try it.

[First.officer]

Have to agree with His dudeness.....one of my concerns if starting without the ITT indication is that although unlikely, you don't have an indication of how quickly/slowly the trend is proceeding with regard to a possible hot start, or hung start.

[TheiC]

Just sharing a thought, after reading first.officer's post: the first clues of an impending hot or hung start are generally in the fuel flow and spool speeds, though I've noticed that not many people pay close attention to fuel flow during start.

The ITT tells you what is happening as a consequence of fuel flow and acceleration.

[First.officer]

TheiC....thanks for that, have to admit i'd concentrated purely on one area when starting the 525 in relation to the OP's question - care to elaborate further on what to look for with regard to fuel flow and hot starts ?.....got to admit my increasingly poor memory and lack of flying means i'm forgetting loads these days, so would be nice to get some pointers as to what to look for in future....like tesco, "every little helps" lol.

[TheiC]

I'm struggling to remember the numbers (70 or 80 lbs on first introducing the fuel springs to mind, and about 140 when stable), but I would suggest you watch some normal starts and see what you get - then, if you see something different, you know that you may be about to have a problem. Acceleration is another matter, but try counting the N2 numbers 'out loud' but silently, every 10% or 5%, and get comfortable with the cadence...

My own drill is as follows, again, if the grey matter is functioning:


before start checklist complete
area clear
ground crew signals
check visually from flight deck
press start button, check electrics look correct
12% N2 and some N1 rotation, put the fuel in
check fuel flow
monitor light-up
monitor acceleration, fuel flow, and ITT
(monitor starter disconnect, having worked out beforehand whether you'll deal with a problem by memory or from the QRH)
check stable (with a green light if not a + aircraft)
I also notice some people have a finger hovering over the starter disengage during start (I even had one experienced chap move his finger there rapidly just after we put the fuel in, which was a bit of a shock!). This has always struck me as a very bad idea, as the very last thing you are going to do is press that button in a hurry. One hand on the throttle, with finger ready to operate the gate, ready to take the fuel out, but the other resting on your lap or operating the stopwatch, if your SOP is to time your starts.

While there are strengths and weaknesses in doing your training on an aircraft rather than in a sim (and I don't know which applies to your operation), a definite strength of the sim is that start malfunctions and abnormalities can be trained effectively without hazarding the aircraft.

Hope that helps, and also that someone will correct me if my memory is indeed not up to scratch today!

[flugzeug]

@his dudeness: No question about the ITT on start, just that I guess I didnt explain myself correctly. The topic of this thread is about the "ITT Fail" indication with engines not running and cold weather, and wether the FADEC would prevent the engines to start when there is an indication missing. This ITT Fail signal comes from the FADEC.

The same thing happened to me, and just the same way you can bring the flaps up without having to start the engines, just pushing start and leaving the throtles on cutoff. We pushed "Start" and on that moment the Fail light extinguished. Wich allows you to continue with the normal start procedure just like TheiC nicely explains.

Pls correct me if I am talking nonsense.

Rgrds,

[eckhard]

12% N2 and some N1 rotation, put the fuel in

TheiC, I think the FADEC engines on the + CJs allow thrust lever to idle before N1 rotation. There should however be N1 rotation before 25% N2.

Otherwise your memory seems fine to me (and I'm not a shining example of a good memory!)

[TheiC]

eckhard,

You're quite right. I also didn't mention oil pressure, which some people get very excited about...

Maybe a good time to remind ourselves of the wind limits on starting these little jets! (I miss them; some of my most enjoyable flying has been in CJs!).

[Cough]

Just a thought, from someone outside the CJ world...

The EGT indication on our engine warms for the first start of the day, the best I've ever seen is -21 in Oslo up to +5 prior to chucking in the fuel. Now if heat helps the engine gain its ITT indication, what would be wrong with a dry run prior to the engine start? As the compressors start doing their stuff, the air in the engine will warm and may bring the ITT into life??....?? (sufficient electrical energy aside!)

[TheiC]

sufficient electrical energy aside

Now, that's one thing I don't miss about these little jets :ok:

(Cough, they suffer from tiny batteries and, especially in the cold, it's always a worry until the first generator is on line!)

[His dudeness]

@flugzeug: your talking sense...I overread the part: "The moment we pushed Start, the indication became normal."

[Cecco]

Due to the cold weather, the microprocessor can cause the indication you saw on both aircraft.

We recommend turning the battery on for a minute, then turn it off and then to cycle power.

This procedure is located in TASK 71-00-00-760-830 "General Operating Procedures" of the FJ44-3A-24 and FJ44-1AP Line Maintenance Manuals. If you scroll down to number "6. Abnormal Operating Procedures", it states that if the FADEC is below -40 degrees Fahrenheit at start up, it may need to be power cycled after being turned on for a minimum of 3 minutes to reset it's microprocessor.

As you said after a while having the power turned on, the indication disappeared. We recommend operating the engine AFTER the indication has disappeared so that the FADECs operate properly due to the cold weather.

[RainingLogic]

OP: You should be fortunate that your boss isn't that sharp and hasn't pondered why you left the plane out all night long in the weather.