yaw damper during x winds

[snorkboggler]

I was doing an OPC the other day when the check pilot said turn your yaw damper off at minimums and I said we can land with it on a LEAR 45.

So he said I know you can but its good to keep your feet in practice for the strong crosswind landing one day...mmm okay what does everybody else do in this plane?!

S

[Empty Cruise]

If the '45 is certified with YD on for T/O and LDG - then I'd be willing to bet my bottom buck that the max demonstarted XWC has been achieved with the YD switched on.

Is it a Bombardier checklist item? Is it in the AFM? What if a go-around is initiated below minima?

You can probaly see where this is heading...

[snorkboggler]

Its the one where it is approved and no mention of it on the landing checklist. I have to say i can see both sides of the story.

[Bruce Waddington]

Hi Snorboggler,

In our operation we turn the Yaw Damper off for landing.

The Lear 45 manuals are not the best I have worked with and you must read between the lines a little to understand why we believe there is a requirement to have the Yaw Damper off for landing .

The Limitations Chapter of the FAA Approved Flight Manual states that;

"On aircraft 45-002 thru 45-225 NOT modified by SB 45-55-6, the yaw damper must be engaged for all flight operations except take-off and landing."

"On aircraft 25-226 and subsequent and prior aircraft modified by SB 45-55-6, yaw damper use is not required."

So, there is no clearly stated prohibition against landing with the Yaw Damper on but the implication is there that it should be off for take-off and landing . Also, in the FAA AFM there is no requirement in any normal or abnormal checklist to turn the Yaw Damper off for landing which might lead you to beleive that landing with the Yaw Damper on is ok.

But, and this is a big but, if you choose to leave the Yaw damper on for landing something happens during the landing roll ........

Your job is to get into the systems chapters and tell me what that is :-)) I think then you will agree that the Yaw Damper should be off for landing

I look forward to reading the results of your search.

best regards,

Bruce Waddington

edited for spelling error

[buger T]

If I caught the wrong tone in your post my apologies but the whole what if something happens in the landing roll....well what if it does personally I would want to land with it off.

[john_tullamarine]

On aircraft 45-002 thru 45-225 NOT modified by SB 45-55-6, the yaw damper must be engaged for all flight operations except take-off and landing. On aircraft 25-226 and subsequent and prior aircraft modified by SB 45-55-6, yaw damper use is not required.

No background on Type and no knowledge of the systems so my comment may be old cobblers ..

The AFM statement read as a certification thing appears not to have the implications suggested above. To me it reads quite simply -

(a) on premod early serials, you MUST have Y/D ON other than for T/O and landing. You can choose whether you have it ON for T/O and landing. More usually, one would just leave out the last bit.

(b) later and early postmod serials Y/D is optional.

In general, AFM limitations are to be read quite literally and ought never require any "reading between the lines"

[Miles Magister]

Yaw Damper

SB,

If you have the YD on for landing the system will automatically counteract any yawing moments. This means that when you kick off the drift the system will oppose you thus reducing your control of the aircraft.

Make your own decisions, but I select it off at DH.

Regards

MM

[Victor India]

Agree fully with j_t.

Making assumptions about what the aircraft limitations imply, without explicit statement, is nonsense. Just because something doesn't NEED to be on, does not imply that it MUST be turned off.

Most importantly, if the Operating Manual/Checklist doesn't dictate an action (as significant as disengaging an aircraft system), it should not be done.

Miles - you can rest assured that unless the manufacturer says it MUST be turned off, the aircraft was certified with it turned on.

Most of us are pilots, not TEST PILOTS. Follow the procedures in your Operating Manual unless you feel like becoming a test pilot!!

VI

[Bruce Waddington]

All,

Miles Majister has it correct.

The Lear 40/45 Flight Controls System Chapter issued by Flight Safety, and based on information obtained from the aircraft manufacturer's Pilot Manuals and Maintenance Manuals, states the following on page 15-10;

"With the yaw damper engaged, the yaw servo generates small automatic rudder inputs to reduce and/or eliminate unwanted yaw oscillations in flight. Though not a specific callout in the crew checklist, the yaw damper should be disengaged prior to landing to eliminate undesired yaw damper feedback."

regards,

Bruce Waddington

[FlyingDOM]

The bottom line is that, as it was pointed out in the limitations section, it's not required to be on during T.O. or landing. In fact for the first few years that the aircraft was in service, the limitation was yaw damp was required to be off for takeoff and landing because the rudder boost was required to be on for takeoff and landing and the limitations prohibited the yaw damp and rudder boost from being on at the same time. So after each TO and before each landing the pilots were required to turn off one system before activating the other system. I've been flying the Lear 40/45 as PIC for nine years and the few times that I forgot to turn the yaw damp off before landing it was a very uncomfortable sensation to feel the rudder pedals fighting all my inputs. Very disconcerting to say the least. Works much better in all situations to have the yaw damp off for takeoff and landing, especially in a crosswind situation.

So, in response to the "It must have been certified with the yaw damp on for takeoff and landing.", the fact is that it was originally certified with the yaw damp off for takeoff and landing.

Hope this was helpful.

[Victor India]

OK - I stand corrected regarding the certification issue when referring specifically to the Lear 45.

However - I stand by my comment that the Operating Manual should be followed. If pilots feel the need to "band-aid" procedures and checklists (based on personal experience/preference) without endorsement from the OEM, scope exists for larger and larger deviations to occur as time goes on. This problem is often common among small operations with no significant standards department.

Having faced similar discrepancies (between the Limitations Chapter and Operating Procedures) before, I can say that Bombardier were receptive to the suggestion of a correction and it was done with appropriate process. Having said that, I do believe that Bombardier manuals are far from consistent in many areas.

If an accident occurred in the takeoff or landing phase, even if it was unrelated to the lack of yaw damper, I for one would not like to explain why I was contravening the Operating Manual, perhaps risking my job or the insurance.

Raising concerns with the OEM via the appropriate channels is one of our responsibilities as professional aviators.

VI

[Bruce Waddington]

Victor India,

You write, "If an accident occurred in the takeoff or landing phase, even if it was unrelated to the lack of yaw damper, I for one would not like to explain why I was contravening the Operating Manual, perhaps risking my job or the insurance."

The point is as mentioned in the Limitations Chapter of the AFM;

"On aircraft 45-002 thru 45-225 NOT modified by SB 45-55-6, the yaw damper must be engaged for all flight operations except take-off and landing."

"On aircraft 25-226 and subsequent and prior aircraft modified by SB 45-55-6, yaw damper use is not required."


Clearly the yaw damper is not required for landing and that is why many operators turn it off in accordance with the Lear 40/45 Flight Controls System Chapter issued by Flight Safety. Those who leave it on struggle with the undesired yaw damper feedback and in my opinion are creating a potential for serious problems during the landing and rollout.

regards,

Bruce Waddington

[potatowings]

LR40/45 yawdamper

I flew the Learjet 40/45 and am aware of the issue that has been raised. Both Bombardier and Flight Safety train the pilots to turn the Yaw damper off. As stated above, the reason is that the yaw damper will fight the pilots rudder pedal inputs during a crosswing landing and during the landing roll. This is true on the early premod models and the latter models with the mod integrated at manufacture.

All the SB 45-55-6 does is stops the rudder boost and the yaw damper fighting with each other and does not stop the yaw damper working.

This is in complete alignment with my personal experience. I was once operating the 40/45 with a strong crosswing, maybe 15 to 20 knots and we missed the yaw damper off final check before landing. Needless to say that the rudder work was more than a handfull (or is that foot full??).

Some larger Bombardier bizjets, stipulate that the Yaw damper should be turned on on stand and turned off once you arrived on stand. What the system does in reality was keep the yaw damper off until some pre-determined criteria and then turns it on, and on landing, turns it off when close to the ground.

I hope this helps.

[FlyingDOM]

I think that this thread is a perfect example of why large modern aircraft require a type rating that is only awarded after very thorough, detailed and specific training on that make and model of aircraft. At some point the powers that be decided that these aircraft were far too sophisticated and technically complicated to allow anyone to fly them just by studying the Aircraft Flight Manual. The original equipment manufacturer (OEM), along with the guidance of the manufacturing country's aviation authority, creates and approves the type rating and SIC training curriculum. So, if the training facility is instructing pilots to turn a certain system off during a certain phase of flight, then that is the correct, approved, safest and obviously the most accepted practice for that aircraft. In addition, the pilot in command is the final authority as to the safe operation of the aircraft. At the risk of stepping on any toes, it begs the question of whether a certain contributor to this thread has ever acquired a type rating on any aircraft...

[clivewatson]

This is a perfect example of a thread that demonstrates that many pilots flying corporate jets have absolutely NO idea what their feet are for!

If one is unable to detect whether the YD should be ON or OFF for a landing, they should not, IMHO, be flying anything more than a Cessna 152! Yaw damper is NOT designed to assist flight at approach speeds - in fact it hinders.

By all means follow the destructions (sic) contained within your FM's, but try to land with the YD engaged in anything more than a 5 kt X wind (irrespective of what the FM states), and your feet will be be working far more than they need to be - unless you are of the type who is happy to slap it down any old how.

YD is a pain in the arse for anyone who wants to hand fly an airplane at slower than cruise speeds - and especially for pilots who know what the ball (balanced flight) means.

And in GO-AROUND MODE it's a night mare!

[733driver]

Bold statement clivewatson, and certainly not true for all airplanes. On the 737 we never turneed off the YD in normal ops. And neither on the Falcons. Not reuired or reccomended in the AFM.

It may be true for the Lears. I am happy to admit I know nothing about them.