BeechJet Question

[IFLYHI]

Hey All,
I'm flying a 1997 400A. When applying full power for takeoff, the cabin VSI momentarily indicates a 1500 to 2000 fpm descent. After a few seconds, it stabilizes at about 200 - 300 fpm descent. While taxiing, we get 1000 fpm descents when adding power, and then 1000 fpm climbs when pulling the power back to idle. The mechanics are saying they think this is normal. Its been a while since I flew any other beechjets, but it seems excessive to me.

Are both safety valves supposed to be fully open on the ground? Any thoughts???

Greg

 

[marqmarq]

limits

I experienced the same problem in the Ultra. I learned that the MX limit is +/- 600 fpm for Ultra. 1500+ feet might be normal, but I bet there is a limit somewhere.....

 

[DO-82 driver]

I had a similar thing happen to me in an XL.

It was an outflow valve.

 

[fischman]

Yup. It sounds to me like you have stuck outflow valves. Keep an eye on that dif. press. up at altitude.

 

[brokeflyer]

Write it up.......problem solved.....unless your the MX guy too.....

 

[400A]

Go to "Both High" on your bleed selector and see if it stops. We had a 1992 model that did not do it, but our 2000 model does. Flight Safety says it has something to do with a change they made that allows you to get so much more airflow from the eye-balls than the older models did. The change was made somewhere around RK-110. It will also do it in flight at lower altitudes and lower power settings. You will feel drastic flow changes from the eye-ball's a you move the throttles at low power settings. When you go to both high the airflow and pressure remain very stable. I have only flown 2 or 3 Post RK-110 units but they all did it. Isolating to 1 bleed will also stop it, but I like the extra airflow. The Auto temp modes also work great now that they are digital. It also limited how much change the folks in the back can make with their controller. Hope that helps.

 

[CaptainSpaz]

Hi,

I have flown every model from a single digit serial number Diamond Jet to factory new Hawker 400XP.
Former IP for this type.

This is not normal. Write it up. Something is broke.

And you thought I was going to give you an answer to what is wrong or five different ways to try to "fix" the problem?

 

[dime line]

Hi,

I have flown every model from a single digit serial number Diamond Jet to factory new Hawker 400XP.
Former IP for this type.

This is not normal. Write it up. Something is broke.

And you thought I was going to give you an answer to what is wrong or five different ways to try to "fix" the problem?

You have to work for FLOPS. LOL

 

[CaptainSpaz]

No FLOPSing around here!

 

[ToTheStars]

You probably have a phneumatic relay that has failied. However, it also could be an outflow valve or pressurization control.

The phneuamtic relay is the weakest link. If your'e flying an older serial no BJ, they have modified the relay and your cabin pressurization will act slight different w/ the new relay.

You do need to get it fixed as the other posters have noted. I don't recommend continued flight w/ a degraded or failed system.