C20r Hot Starts

[machinegun kelly]

Anyone else experiencing hotter starts with their recently overhauled FCU's? Looking into some info on this problem, and reports of a different type of bellows being installed in the FCU at OH.

Does anyone else have input, stories, or rigging tips on this problem?

 

 

[Heliian]

First, check fcu for correct p/n. Make sure throttle rigging is correct and set start adjustments to the nominal settings iaw rr250c20r mm. Check fuel nozzle for cleanliness and correct operation, Check airlines for leaks using dry air iaw rr250c20r mm, Check inline check valve to nozzle for correct operation. Check pilot's starting procedure, DO NOT wait for N1 to top out before introducing fuel, open throttle at close to lowest N1 speed permitted for current OAT as per the correct flight manual, depending on a/c type you may need to reference a FM supplement. Max.flow setting should be at scribe mark, but this adjustment should not be touched. Most FCU's respond well to small adjusments on the st.accel and st.derich, I have seen an FCU come out of o/h with internal problems and would just dump fuel no matter what the adjustment, always too hot but this is very rare. Unless it came from some bargain shop, most other places flow check their fcu's prior to delivery. Worst case scenario, swap it out and try again.

 

What are your first and second peak temps? how long is it taking to start? The C20's like a fast and warm start, i like to set mine so that the tot goes into the yellow near the top but not into the red or transient range, leave the extra room for pilot error or a weak battery. Good luck.

 

 

[nutmix]

I have had starting issues with o/hauled and new FCU's on C20R's. The main cause is the bellows shaft scoring. This will give you slow acceleration from 30-33% onwards especially on the first start of the day.

 

Regarding light off temps on R's. There is a CSL given to me by the RR rep that tells you that a R should start up to 50 degrees hotter than a B. The CSL states that the correct temp for a normal start should peak at 860 degrees which is 50 deg above red line (scarry the first few times with a Diamond TOT indicator as the scale expansion makes the needle seem like its going to rocket away). Remember that the transient should be under 10 seconds.

 

I have found that the first start of the day will be slow but will stay below red line but any further starts, cooled to below 150 deg will have a first peak of approx 650-660 deg and a second stage peak of approx 850-860. It will transit for approx 6 seconds. The RR rep has assured me this is a good start. Total start time should will be approx 30 sec's.

 

I will find the CSL number and post it later.

 

One thing to be carefull of is that you dont have the start de-rich nearly at the upper limit and the accel at the lower limit. This can lead to compressor stalling.

 

The aircraft are MD500N's.

 

Hope thios is some help.

 

Nutmix

[machinegun kelly]

I have had starting issues with o/hauled and new FCU's on C20R's. The main cause is the bellows shaft scoring. This will give you slow acceleration from 30-33% onwards especially on the first start of the day.

 

Regarding light off temps on R's. There is a CSL given to me by the RR rep that tells you that a R should start up to 50 degrees hotter than a B. The CSL states that the correct temp for a normal start should peak at 860 degrees which is 50 deg above red line (scarry the first few times with a Diamond TOT indicator as the scale expansion makes the needle seem like its going to rocket away). Remember that the transient should be under 10 seconds.

 

I have found that the first start of the day will be slow but will stay below red line but any further starts, cooled to below 150 deg will have a first peak of approx 650-660 deg and a second stage peak of approx 850-860. It will transit for approx 6 seconds. The RR rep has assured me this is a good start. Total start time should will be approx 30 sec's.

 

I will find the CSL number and post it later.

 

One thing to be carefull of is that you dont have the start de-rich nearly at the upper limit and the accel at the lower limit. This can lead to compressor stalling.

 

The aircraft are MD500N's.

 

Hope thios is some help.

 

Nutmix

 

Thanks Nutmix, that is very comparable to our experiences. I did hear from an O/H shop that new bellows are being installed, and the material has changed. I believe the old ones that worked fine were brass, and the new ones are stainless (I believe). In this scenario, a person has to rig for the first start of the day, or the warmer subsequent starts.

A little more investigation and time for sure.

 

thanks guys.

[snark]

Thanks Nutmix, that is very comparable to our experiences. I did hear from an O/H shop that new bellows are being installed, and the material has changed. I believe the old ones that worked fine were brass, and the new ones are stainless (I believe). In this scenario, a person has to rig for the first start of the day, or the warmer subsequent starts.

A little more investigation and time for sure.

 

thanks guys.

 

 

We have had problems as well with recently overhauled FCU's. Went thru history and all behave similar from mulitple reputable shops. Brass vs Stainless bellows was the explaination from the fine fellows at Essential Turbines. Very knowledgeable with regards to C20R's. They explained to me there is no longer a happy medium due to the new bellows. You can either have a good first start of the day, or good subsequent starts throughout the day. We had been setting the FCU's for a good first start, but the warm starts 860 + TOT gives everyone I know the heeby-Jeebies (Technical for seat cushion sucked into pilots rear). we instead have gone with a poorer start in the morning with a delay of up to 5 seconds between 30-35% n1. First start in the am 30-40 seconds, and surprisingly after turning the TOT effectively down to set for a "warm" or subsequent start our overall start length has decreased to 20-30 seconds, for whatever reason closer to 20. You would think with more TOT would come more coals in the fire to get the hamster moving, but the engines are spooling better with less TOT. Go figure? Long and short you are not alone. C20B's have the same bellows and don't find any abnormal issues with them? Good luck with everything, NOW, How about Governors, anyone getting to 1/2 life without removal?

[nutmix]

We have had problems as well with recently overhauled FCU's. Went thru history and all behave similar from mulitple reputable shops. Brass vs Stainless bellows was the explaination from the fine fellows at Essential Turbines. Very knowledgeable with regards to C20R's. They explained to me there is no longer a happy medium due to the new bellows. You can either have a good first start of the day, or good subsequent starts throughout the day. We had been setting the FCU's for a good first start, but the warm starts 860 + TOT gives everyone I know the heeby-Jeebies (Technical for seat cushion sucked into pilots rear). we instead have gone with a poorer start in the morning with a delay of up to 5 seconds between 30-35% n1. First start in the am 30-40 seconds, and surprisingly after turning the TOT effectively down to set for a "warm" or subsequent start our overall start length has decreased to 20-30 seconds, for whatever reason closer to 20. You would think with more TOT would come more coals in the fire to get the hamster moving, but the engines are spooling better with less TOT. Go figure? Long and short you are not alone. C20B's have the same bellows and don't find any abnormal issues with them? Good luck with everything, NOW, How about Governors, anyone getting to 1/2 life without removal?

 

Yeah, it is a well known fact the inconell bellows are too stiff. They exercise them 10,000 times before installation to try and soften them. One thing is that the FCU performance gets better the more hours you do, but you can be forever adjusting that start temp.

 

Maybe the B's dont suffer as much as the compressor doesnt take anywhere as much grunt to spin up as the R's.

 

Dont start on the new and improved governors, they are terrible. The best time Ive had was a new C30 one which got to an amazing 1200 hrs. I think the average would be approx 900 hrs before failure. You can normally tell when they are on the way out when the pilots report that the beep range has shifted.... when you adjust to get it back you find the pointer is at or above 80 degrees, then you've got about 100-150 hrs. Ive had B ones fail as as early as 35 hrs! The scary thing is when they are removed you cant actually turn the shaft's. I know that if I had a box of old style gov's they would sell like hotcakes.

 

Good luck to all

 

Nutmix

[skidkicker]

Nutmix. I can say today I learned something. Sounds like you have those FCU's down pat.

 

I hope I can help too.

 

This is from Essential Turbines that if you put your start ac-cell to nominal (I think 3 from the left)and turn your start de-rich all the way down (counter clockwise) then start the engine. It will hang at around 20 percent I think. Then turn the start de-rich clockwise until the engine starts to accelerate. This procedure sets up the optimal start de-rich schedule. Don't touch the de-rich anymore and adjust for start accel for the next start t for acceleration from 30-33 %

 

I think I speak for everyone that the C20R's are finicky to start and adjustments should be made in minimal increments.

[offset]

The CSL mentioned earlier is CSL 4050 for the C20R. The CSL 1176 for the C20B.

The settings are listed and it has a wealth of good information I have a copy of it with me to reference from time to time and it comes in handy. It came out in 92 but still seems relevant for the most part. Not taking the new overhaul techniques and materials into consideration.

Lots of good tips in the earlier post.

 

The C20R is a different breed of animal compared to the C20B, thats the bigest issue pilots jump in and treat them the same. It tends to turn on that red light on your TOT gauge more than usual.

 

Offset