Max speed differential

[Dariuszw]

CJ I fly has single pilot setup with PFD on the left and conventional instruments on the right. According to AFM max difference between two airspeed indicators is 4kts however during 80kts check its more like 8kts. I would like to know what is the maximum allowable speed difference between two primary airspeed indicators before abort should be initiated. Any official reference is greatly appreciated. Thank you in advance !

[Herod]

Like I said on your previous thread, why not ask the manufacturer? Oh sorry, you did via the AFM. If it says 4 knots, why do you think there should be another speed hidden away somewhere?

[john_tullamarine]

Although you might find the occasional reference to ASI split limits, the more usual limitation is altimeter difference. The two are connected by static pressure and the errors are related.

From a practical point of view, up to 5 kts delta generally seems to be accepted on the basis that much more provides for multicrew confusion and difficulty in co-operative working in the cockpit.

[de facto]

And i how do you crosscheck such a small speed difference? One eye on your side and the right eye googling the other side?:8

[Denti]

Lazy guys like me simply wait for the IAS DISAGREE message on their PFD and then run the checklist for it. Constantly cross checking the other side and the standby instruments is probably asking a bit too much, although an occasional glance to crosscheck all indications is not a bad idea.

[500 above]

Denti, I don't think he has IAS DISAGREE, that's probably too advanced for FS4. Maybe FSX has it?

[Dariuszw]

Ok, just to answer my own question to the benefit of humanity which I will gratiously include most of you bus drivers:cool:.... max speed difference between to primary airspeed indicators must be 10kts !

Now you just learned something from seventeen year old who unlike YOU is flying a sport car ! Be ashamed !:hmm:

[de facto]

On the 737, 5 kts will trigger the IAS disagree.
Darius,what is the 80 kts check for in your single pilot cessna jet aircraft?I am sincerely interested.

Now you just learned something from seventeen year old. Be ashamed:


:suspect:

Sorry i missed your latest edition:
Now you just learned something from seventeen year old who unlike YOU is flying a sport car ! Be ashamed
:D

[Brian Abraham]

Sorry i missed your latest edition:Don't worry de facto, Dariuszw is our old friend SSG who we know to have zero experience in any aeronautical piece of machinery.

[Dariuszw]

Ahhh jaaah... the usual suspects;)

jealous, jealous, jealous of my sport car!!!

[FCeng84]

Airspeed displays all involve some level of filtering to avoid having the display jitter excessively when flying through turbulence. This filtering introduces a response delay when airspeed is actually changing such as during a takeoff roll. If two airspeed displays have different levels of damping or filtering, during an acceleration one will lag actual speed more than the other and thus the two will exhibit a "dynamic" difference.

I think of much more concern is how the two displays compare when flying at constant airspeed. In that situation delays associated with signal filtering will not contribute to observed differences. When at constant airspeed, comparison of two airspeed displays reveals the "static" difference.

I would imagine that any guidance regarding acceptable differences between airspeed displays is targetting "static" and not "dynamic" differences.