Bell 412 start and performance questions

[threesix]

start procedures

there is really no issue here if you want to fully open the throttle and then go idle then click the detent and put it just below idle. In fact, i l learned to appreciate the value especially if ive just made a shutdown of engines and my passengers decided to board again after around 3 to 5 minutes. I just do the procedure however i doubled the position of throttle from the idle detent so as not to have a high ITT. Never had a problem after so many thousand starts...

[Blackopsrider7]

Bell 412EP run up snag.

Hi 412EP pilots and maintainers. A friend of mine was doing a run up on a 412 Griffon, and this is what was happening. One Power Section(PS) was at 71% N2, he went to roll up the other PS and the one at 71% dropped down to 61% essentially idle. He reversed the PS's and tried it in the reverse order, and the power section at 71% again dropped to 61%. PS are PT6T-3Ds. What is your take on this? Thanks.

[212bushman]

G'day Bor7,
we had something similar to what you have. On our 3D's, the start sequence kept us guessing for a while. Whilst bringing up #2 eng, (#1 up & running). #1 would drop back to idle. We checked rigging , did PA's etc. Nothing out of the ordinary. Then we swapped AFCU's. Problem swapped , hence culprit found. (I am not sure why your snag alternates as per which one you bring up to match the 1st one up though)?
Hope this helps,
212bm.

[Blackopsrider7]

Thank you BM. I will tell the guys, to start there!

[Blackopsrider7]

Bell 412EP

Hi folks, we are having an issue with a B412EP that has PT6T-3D power sections. We can't seem to get our accel checks times down enough. What we have done so far is switched out the TCU(-01), cleaned the P-3 filters. Checked for air leaks. Our accel times are running around 6 secs to low of 4.99 so needless to say for the altitude and temps, we are not meeting our times. we have maxed out our dome adjustments( 6 clicks on this one) and only get a difference of 0.5 sec. This is both power sections, we did a power assuarnce and our temps are good, ITT margin is good...running out of options save switching out AFCU or bleed valves. Question two is will a -01 TCU cause issues with running -2 governors? There is a bullentin out, but for some reason we got our twin pac shipped like this. Any takers/advice on this one? Feel free to PM me.Thanks.

[Miamijerry]

Slow accel times, change the ACFU's.

-1 and -2, part numbered N2 gov's and TCU's can NOT be intermixed.

[cbox chip]

Is that to say that -1 and -2 N2 governors cannot be intermixed either?

[Miamijerry]

-1 N2 governors and -1 TCU are a set

and

-2 N2 governors and -2 TCU are a set

Don't mix -1 and -2

[erang5]

BH412 vs BH412SP hover performance

Hi all,

My company operates Bell 412SP with a BLR strake kit on their tail as well as early model a/c which are basically 212 with 4 blade rigid rotor which are called by some IGW ( Increased Gross Weight)
The so called IGW a/c have better hover and takeoff perf. (the basic weight is the same as the SP a/c). some pilots estimate the differences being more than 5% Tq

Does anyone have any insights as to why that might be?

I am also looking for hover performance charts as opposed to the max weight for hover that is provided in the civilian flight manual, any idea where to get such charts?

Thank you
Eran

[cbox chip]

Well the 412 "classic" has a smaller fuel system than the SP (5 cells versus 8) so I suppose it might be a bit lighter but I really can't imagine how it would outperform the newer bird with strakes (but no fast fin?)

Does the straight 412 read mast torque or is it the same as a 212 where it takes the total of the two single engine torques read at the c/box?

I don't know how it is on 412's but on 212's the difference between a good set of M/R blades and a bad set can be quite noticeable.

What are the empty weights of these machines?

[erang5]

cbox,

Thanks for your reply

as far as i know the Tq measure system is identical to the latter classic 412. It is same as the engines (PT6-3B) and lifting system...

Since we have 2 a\c of each type and they act quite similar I don't suspect malfunction

GW is the same despite the empty wight differences

[Encyclo]

Just the facts

412 'classic' has five fuel cells, similar to the 212 and holds roughly 220 Gal.
412 SP/HP/EP has 10 cells, six in the floor, four in the back for about 330 Gal

The 412 'Classic' and 412SP use the torquemeters off the Cbox to read torque, eng1 + eng2= MGB Tq

The 412HP/EP use torquemeter for eng Tq but phase shift mast for mast Tq, so eng1 + eng2 is not necessary equal to mast Tq.

Typically, worn/eroded blades don't have a big effect on performance for the 412; what you see in the charts is what you get.

Back to my coffee

[cbox chip]

Interesting info there. So the 412 linefrom oldest to newest goes 412 classic, 412SP, 412HP then 412EP?

So many variants jeez there's only one 212 ( well I guess two if you consider the HP kit). What I meant about good and bad blades was more how well a particular set flew together not age or erosion damage.

[Encyclo]

Roger that Cbox,

I have heard of an operator swapping a set of 212 blades to compare; same day same helicopter and measured about 500 Lbs more capacity for the same torque.

Haven't heard of that with 412s

[Chickenpool]

Question about procedure of Bell 412 ?

Why before start engine,pilot must RPM INCR/DECR switch........DECR FOR 8 SECONDS?
and what is 8 second ?

Thank you for answer

[Ascend Charlie]

So that the N2 beep is fully down before you get to open the throttles fully. This can prevent an overspeed in some cases - it may have been accidentally beeped all the way up while the engines were off.

And 8 seconds is 2 seconds less than 10 seconds...

[Chickenpool]

thank you for answer and relax (++!)