Reverse altimeter indications in a Lear

[PB4UGO]

In the Learjet (or other jet, the Lear is all I've flown), what causes a slight altitude indication in the opposite direction immediately following a pitch change? Is it altimeter reversal error from false static pressure sensations or is it a result of the tail contributing to the total lift on the aircraft?

 

[avbug]

It is a static positioning error.

 

[414Flyer]

Coriolis forces. Its reversed in the southern hemisphere

 

[Jeff Helgeson]

Quit flying inverted.....

.....or start flying inverted, whatever works for you.

 

[FN FAL]

Coriolis forces. Its reversed in the southern hemisphere

or PIO?

 

[banned username 2]

I thought it was because of the EMP Gun...

 

[leardrivr]

It is the static error. The static system design for the lear was kind of weak. When the static default correction modual takes a dumb it is even worse. But don't worry. If your lear is getting an rvsm upgrade it will solve this issue. Makes it much easier to hand fly at altitude also. I flew the first rvsm aproved lear 20 series aircraft last year. It is fantastic. Autopilot works like a champ. It dosn't seem like flying a lear anymore. It will be hard to get used to. The company I was with has the first group cert. for instalation. They had completed three aircraft before I left and they all worked good. one 24B a 24 and a 25B. I think they have 8 or 10 of them done now.

 

[FracCapt]

If your lear is getting an rvsm upgrade it will solve this issue. Makes it much easier to hand fly at altitude also.

Just remember....one of the RVSM requirements is that the autopilot be flying the aircraft at and above FL290. Hand flying at altitude(or long, high altitude trips with an MEL'd autopilot) will be a thing of the past.

 

[PB4UGO]

Thanks for the input, that answers my question. We plan to get it RVSM'ed in December, I can't wait because our autopilot has so many bugs. (As do most 25 autopilots) I want to keep the old one for target practice!

 

[wings421]

It is the static error. The static system design for the lear was kind of weak. When the static default correction modual takes a dumb it is even worse. But don't worry. If your lear is getting an rvsm upgrade it will solve this issue. Makes it much easier to hand fly at altitude also. I flew the first rvsm aproved lear 20 series aircraft last year. It is fantastic. Autopilot works like a champ. It dosn't seem like flying a lear anymore. It will be hard to get used to. The company I was with has the first group cert. for instalation. They had completed three aircraft before I left and they all worked good. one 24B a 24 and a 25B. I think they have 8 or 10 of them done now.

RVSM is very sweet.

 

[leardrivr]

Just remember....one of the RVSM requirements is that the autopilot be flying the aircraft at and above FL290. Hand flying at altitude(or long, high altitude trips with an MEL'd autopilot) will be a thing of the past.

I am aware of that. I was just pointing out to this gentelman that for now (you can still hand fly the aircraft at FL 410) hand flying with the rosemont probes, air data computers, digatal altimeters, and the new static system is a breeze compared to the old system. Some one who is used to hand flying the airplane with the old equiptment can easily hold 20 feet hand flying with the new system. Not that I would suggest someone consider this a viable way to operate the airplane once rvsm goes into effect. Who would want to. A reliable autopilot is a wonderful thing!

 

[avbug]

The Learjet was never a bad hand flyer at altitude to begin with. Any improvements are certainly welcome...but I've been hearing for years about how unstable or "slippery" the airplane is, and it's a load of hogwash.

Why would someone want to handfly it? Because one could easily die of boredom after turning it over to the autopilot. Because I didn't get into aviation to not fly. Because one should hand fly enough to stay current with the airplane. To keep from going to sleep. Because the learjet autopilots have never been what one would call stellar...especially in the 20 series. Why not?

 

[leardrivr]

The Learjet was never a bad hand flyer at altitude to begin with. Any improvements are certainly welcome...but I've been hearing for years about how unstable or "slippery" the airplane is, and it's a load of hogwash.

Why would someone want to handfly it? Because one could easily die of boredom after turning it over to the autopilot. Because I didn't get into aviation to not fly. Because one should hand fly enough to stay current with the airplane. To keep from going to sleep. Because the learjet autopilots have never been what one would call stellar...especially in the 20 series. Why not?

I agree with completely. I have never found the lears handling charecteristics to be unstable or "slippery". I'm sure you would hear most of these fables from pilots who have not actualy flown the airplane or just flew it poorly. I will miss hand flying the aircraft very much. Actualy I miss the aircraft altogether. It is a very speacial bird. I flew lears for 3000 hours and I did learn one thing. If you are flying with a pilot with marginal insturment skills. Not having an aoutpilot sucks! If you ever had to sit there and watch someone struggle to hold +/- 300 feet at 410 wondering if he going to get you busted is a real drag. Being able to have the guy let iron mike drive at altitude is better than watching him like a hawk for 2 hours. Unfortunatly like most 135 ops the management will put a warm body next to you if that is all they have to choose from at the time they need a new hire. I'm sure you probably have experienced this yourself. I only used the autopilot in cruise when I was tired and always hand flew my approaches. Thanks to rvsm and fly by wire the day's of stick and rudder flying are numbered.