To pitch trim or not to pitch trim...

[gwav8or]

I've started getting quotes for a GFC500 autopilot for my '67F.  I already have the 355 GPS, 345 transponder, dual G5 install.  I just got the first quote.  The shop quoted the GFC500 install with 3 servos - pitch, roll and pitch trim.  The pitch trim adds about $3,400 in hardware cost.  Unsure of the additional labor to install pitch trim but total labor (including pitch trim) was 60 hours.

Labor cost sounds about right to me but I'm no expert.

Total parts quote was just shy of $16k.

Is it worth the extra 3k (plus labor) to add the pitch trim?

Also, if there is a servo for both pitch and roll, is a third servo actually required for the pitch trim?  Again, I'm no expert, just asking questions.

I'm also considering the Aerocruze but don't really want this thread to become a Garmin vs BK contest. :-)

[MikeOH]

I suppose the responses are going to come down to what someone is used to.

I have an STEC-30 with altitude hold. No electric trim (thus, no pitch trim) and I don't miss having it at all.  Sure, I have to occasionally trim it, but mainly when first setting up for cruise; after that, very rarely.

No way I'd pay what sounds like another $4K - $5K (30% more, in your case) for that marginal convenience.  Plus, you never have to worry about 'run away' trim!

[gwav8or]

7 minutes ago, MikeOH said:

I suppose the responses are going to come down to what someone is used to.

I have an STEC-30 with altitude hold. No electric trim (thus, no pitch trim) and I don't miss having it at all.  Sure, I have to occasionally trim it, but mainly when first setting up for cruise; after that, very rarely.

No way I'd pay what sounds like another $4K - $5K (30% more, in your case) for that marginal convenience.  Plus, you never have to worry about 'run away' trim!

Yeah, I agree it's gonna come down to personal preference. 

And yeah, I'd rather not have to deal with a 3rd servo to die and/or have run away trim.  Plus, I don't mind adjusting the trim.

[Bolter]

58 minutes ago, gwav8or said:

I've started getting quotes for a GFC500 autopilot for my '67F.  I already have the 355 GPS, 345 transponder, dual G5 install.  I just got the first quote.  The shop quoted the GFC500 install with 3 servos - pitch, roll and pitch trim.  The pitch trim adds about $3,400 in hardware cost.  Unsure of the additional labor to install pitch trim but total labor (including pitch trim) was 60 hours.

Labor cost sounds about right to me but I'm no expert.

Total parts quote was just shy of $16k.

Is it worth the extra 3k (plus labor) to add the pitch trim?

Also, if there is a servo for both pitch and roll, is a third servo actually required for the pitch trim?  Again, I'm no expert, just asking questions.

I'm also considering the Aerocruze but don't really want this thread to become a Garmin vs BK contest. :-)

It is an opinion...  For me, investing in the top autopilot upgrade, it should be the full package, or else it will not feel like a modern panel and AP.  High dollar upgrades should be impactful.  Unlike replacing my old JPI 830 with JPI primary 900.  $10k, and it all feels pretty much the same. 

Of course, it depends on what you are used to, and if you really do not want to know better.  I have always had electric trim airplanes, including my trainer Piper (I was spoiled).  When my electric trim went out, and I had to manually tweak the trim for the AP, it became annoying, because I was used to not doing that.  Over time, it became standard practice, and of course it is manageable.  I finally got the AP and trim servo overhauled, and it felt so nice to have full service again.   AP should be set it and forget it (yes, we still scan for safety, but never have to touch anything, is what I mean), especially if you are managing descents and approaches with the AP. 

[Rick Junkin]

1 hour ago, gwav8or said:

Is it worth the extra 3k (plus labor) to add the pitch trim?

Also, if there is a servo for both pitch and roll, is a third servo actually required for the pitch trim?  Again, I'm no expert, just asking questions.

 

I'll answer your second question first. Yes, a third servo is required for autopilot pitch trim. The pitch servo acts on the elevator push rod, the pitch trim servo acts on the trim mechanism.

If you don't install pitch trim the GFC500 will give you a PTRIM advisory on the G5 with an up or down arrow to tell you which way to manually trim the airplane as flight conditions change. If the pitch trim servo is installed the GFC500 trims pitch automatically and you never see the PTRIM advisory unless the pitch trim servo fails.

Where this might make a difference is how the airplane responds when you disengage the A/P on an instrument approach. With the pitch trim servo installed, the airplane will be in trim for your current airspeed and there will be no change in control forces or nose position when you disengage the A/P. If you don't have a pitch trim servo, your manual trimming may be slightly off and you might experience a pitch bobble or excursion when you disengage the A/P. If you're keeping up well with the manual trim this is minimized, but may be an issue in a high workload approach. Whether this is a concern or worth the extra expense is dependent on your assessment of the value of the relative risk mitigation of automatic trim versus manual trim. Either way will work fine with the proper awareness and training. If you're used to manually trimming your airplane then the PTRIM advisories are just added information to augment what you're already doing. But to take advantage of the "Gucci" features and capabilities of the GFC500 you'd want to have the pitch trim servo installed.

[MikeOH]

19 minutes ago, Rick Junkin said:

But to take advantage of the "Gucci" features and capabilities

Ah, THAT's my issue.....I don't have "Gucci" money!

[Matthew P]

Yes, it is worth it, if you are on the fence, have them pre-run the wire and attach the bracket NOW so you can add it later...I even got the YAW damper servo. Once I rotate, engage YD and AP I don't have to mess with the constant changes to the pitch trim..buy once, cry once but yes, the pitch trim is worth the extra, IMO.

[Skates97]

14 minutes ago, Matthew P said:

Yes, it is worth it, if you are on the fence, have them pre-run the wire and attach the bracket NOW so you can add it later...I even got the YAW damper servo. Once I rotate, engage YD and AP I don't have to mess with the constant changes to the pitch trim..buy once, cry once but yes, the pitch trim is worth the extra, IMO.

I had a friend who would say "Buy the best and cry once."

I agree it is worth it. I flew 500+ hours with nothing, not even the positive control wing leveler because they didn't put them in the D's. I like having the trim button on my yoke and being able to adjust trim after taking off, on go arounds, and on approach while leaving my right hand on the throttle. There are times I wish I had put in the Yaw damper servo as well like you did.

[IvanP]

It is largely matter of personal preference. If you can swing it, I would say go for the whole shebang. Adding it later on will cost you more money that if you do it now. I had S-Tec 30 with altitude hold but no pitch trim in my E and was fine doing manual trim for quite a few years. My Bravo has KFC 150 with autotrim and it is lot nicer than what I had in the E. I would not want to go back to manual trim now. Makes flying coupled approaches really nice (I still like to fly approaches by hand, though). 

The potential downside of the autotrim is that it introduces another layer of complexity and possibilities for failure (runaway trim, broken switches/wires, etc..) I had to trooubleshoot the trim circuits couple of times and it was not fun.  

[Paul Thomas]

I don't have electric trim and only have alt hold on my airplane and I'm more than happy with that. Having GPSS is more than I thought I'd have when I first thought about airplane ownership 20+ years ago. While I would use vertical guidance from an autopilot, it's not something I wish for except during approaches.

If I was installing a GCF500, I would want the ability to fly fully coupled approaches. If trim is needed, I'd bite the bullet and do it. If it's just a question of trimming the airplane when it tells me to, it would annoy me to do it but I'd still do it.

Edited July 22 by Paul Thomas

[dkkim73]

Having the AP trim you is a nice workload saver. It's also really more elegant. Do you want the elevator servo potentially constantly pushing on something? Maybe a tech will weigh in, but seems like wear on that servo. 

Getting a GFC500 and skipping that channel seems retrograde to me... Leaving capability on the table. 

If you really needed to pinch pennies I agree with the above, at least lay the groundwork with wiring. And if you install the capstan, you might as well install the motor. 

Data point: My AP went out recently due to failed PTRM channel servo. Still wouldn't not have it. AP out a week to get fixed. The Garmin design is nice in that the clutch/capstan is separate from the servo motor, easier to fix quickly. 

HTH 

[Jackk]

I prefer manual trim personally.

 

 Even flying planes with both like the caravan, I’d use manual pitch trim, just felt smoother and more precise, as fast or slow as I need it too 

[M20F]

I have flown both.  
 
For a Mooney set gear/power/trim at IAF and it just follows itself down.  Take off and trim it follows the speed you want (I climb 120mph IAS with no issue with just a little trim wheel).
 
Saves you money on install, maintenance, and most importantly safety.  Runaway trim, setting to climb at 160kts to FL250, etc. are what kill you. 

I am a huge fan of 2 axis automation in GA but personally I don’t think we are there yet on 3 axis.   History has also proven the third axis to be what kill you. 

[Matthew P]

38 minutes ago, M20F said:

I have flown both.  
 
For a Mooney set gear/power/trim at IAF and it just follows itself down.  Take off and trim it follows the speed you want (I climb 120mph IAS with no issue with just a little trim wheel).
 
Saves you money on install, maintenance, and most importantly safety.  Runaway trim, setting to climb at 160kts to FL250, etc. are what kill you. 

I am a huge fan of 2 axis automation in GA but personally I don’t think we are there yet on 3 axis.   History has also proven the third axis to be what kill you. 

What kills people is not knowing their equipment or tge EPs for the equipment tgey have..technology isn't tge problem, lazy-azz pilots that won't read tge manual and rely on fb are tge problem...my AP came with a CB to pull if there's a serious enough issue.

[MikeOH]

15 minutes ago, Matthew P said:

What kills people is not knowing their equipment or tge EPs for the equipment tgey have..technology isn't tge problem, lazy-azz pilots that won't read tge manual and rely on fb are tge problem...my AP came with a CB to pull if there's a serious enough issue.

If you read your keyboard manual you will find the "h" is located such that you use your RIGHT index finger, not your left

[Matthew P]

8 hours ago, MikeOH said:

If you read your keyboard manual you will find the "h" is located such that you use your RIGHT index finger, not your left

Lol, you are right, that was going to be tge next question I was going to post...now I don't have too

[Pinecone]

14 hours ago, Rick Junkin said:

Where this might make a difference is how the airplane responds when you disengage the A/P on an instrument approach. With the pitch trim servo installed, the airplane will be in trim for your current airspeed and there will be no change in control forces or nose position when you disengage the A/P. If you don't have a pitch trim servo, your manual trimming may be slightly off and you might experience a pitch bobble or excursion when you disengage the A/P. If you're keeping up well with the manual trim this is minimized, but may be an issue in a high workload approach. Whether this is a concern or worth the extra expense is dependent on your assessment of the value of the relative risk mitigation of automatic trim versus manual trim. Either way will work fine with the proper awareness and training. If you're used to manually trimming your airplane then the PTRIM advisories are just added information to augment what you're already doing. But to take advantage of the "Gucci" features and capabilities of the GFC500 you'd want to have the pitch trim servo installed.

And there has been at least one crash where this was a factor.

If you get behind on an approach, you may not be trimming, and when the AP kicks off or you disengage it, you may have a seriously out of trim airplane.

It is NOT like hand flying where you will be aware of the trim being off, the AP pitch servo will "hold the pressure" for being out of trim.

Also, if you keep flying out of trim, the AP will fly fine, but you will be putting more stress on your pitch servo.

[TaildraggerPilot]

You’re going to love the pitch trim / auto trim. Let the GFC-500 be the autopilot it wants to be. 

[TaildraggerPilot]

14 hours ago, M20F said:

I have flown both.  
 
For a Mooney set gear/power/trim at IAF and it just follows itself down.  Take off and trim it follows the speed you want (I climb 120mph IAS with no issue with just a little trim wheel).
 
Saves you money on install, maintenance, and most importantly safety.  Runaway trim, setting to climb at 160kts to FL250, etc. are what kill you. 

I am a huge fan of 2 axis automation in GA but personally I don’t think we are there yet on 3 axis.   History has also proven the third axis to be what kill you. 

Pitch Trim isn’t a third axis, unless I missed something in the past 30 years….

Edited July 22 by TaildraggerPilot
Clarity

[M20F]

43 minutes ago, TaildraggerPilot said:

Pitch Trim isn’t a third axis, unless I missed something in the past 30 years….

Electric trim tends to come with adding up/down to the mix.  Personally I like altitude and heading hold, up/down I prefer myself.  It just takes a small typo or twist if a knob and it becomes a bad day. 

[M20F]

14 hours ago, Matthew P said:

What kills people is not knowing their equipment or tge EPs for the equipment tgey have..technology isn't tge problem, lazy-azz pilots that won't read tge manual and rely on fb are tge problem...my AP came with a CB to pull if there's a serious enough issue.

Mistakes are what kill people.  Instead of twisting 500FPM you accidentally twist 5000 and look at your iPad and it potentially becomes a bad day. 

 

 

 

 

 

[midlifeflyer]

24 minutes ago, M20F said:

Mistakes are what kill people.  Instead of twisting 500FPM you accidentally twist 5000 and look at your iPad and it potentially becomes a bad day. 
 

Yes, mistakes are what kill people. Instead of twisting your heading bug to 100 you accidentally twist it to 010 and look at your iPad and it potentially becomes a bad day. Actually, forget that newfangled heading bug. You heard the instruction wrong and hand flew it to the wrong heading. 

There are hundreds of things we can do with our equipment (and I don't only mean automation)  to give us a bad day (or worst, our last day). 

"Airmanship" includes proper equipment use.

 

[Echo]

I can afford “it”. Juice not worth the squeeze to me.  

[Matthew P]

1 hour ago, M20F said:

Mistakes are what kill people.  Instead of twisting 500FPM you accidentally twist 5000 and look at your iPad and it potentially becomes a bad day. 

 

 

 

 

 

LOL, you just proved my point, if you knew that piece of equipment you would know that you can't twist to 5000 and unless you are blind you would see the rate of descent or altitude you selected in the appropriate "window/location..and then there's the fact you pointed out of people using their iPad as a primary source.

[Matthew P]

3 hours ago, Echo said:

I can afford “it”. Juice not worth the squeeze to me.  

Gotta think resale...a GTN-750, GFC-500...it's a crime not going with the 275s and pitch trim, I can understand if you didn't want the YD..really need to see the differences between what you get with the 275s that you don't get with the G5s..but, to each their own...it will still be a nice platform