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Exchange Autopilot options for a TB20

But nobody will be installing a roll-only autopilot on a TB20. It’s just silly. Various installers, such as we have had on EuroGA over the years, have been questioning the various “low price” claims in the adverts, and few customers have gone public with how much they paid, but in the end the price seems to be in the same region as the old King boxes if you make use of the existing servo mounts.

Looking at this the other way, there is no way Garmin would have come out with a product which so dramatically reduces the amount of money which their dealers make. As the old business saying goes, nobody ever bombs the market. Well, a complete newcomer sometimes does, but these have problems in GA.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

Now, the Garmin website states (check it out) that the suggested MSRP for the basic unit starts at $7495

It does, for a single-axis A/P. And if you seriously believe that the manufacturer’s price includes installation done by another party then, well…

ESKC (Uppsala/Sundbro), Sweden

Peter wrote:

The shop calls back and tells me that the basic unit (2-axis) is $12,300 on the dealer’s price list. And that’s for the simplest (2-servo) unit.
Oh yeah..and Garmin tells him to expect at least 100 man-hours for the install, not including any time spent to remove the old gear. So that’s another $13,000.

Isn’t that supposed to be WITH installation?
25K is bit too much…

EGTR

This was posted on the US TB group, which some may find amusing… European pricing is likely to be substantially higher

Well, I decided to get one of these after watching absorbing as much info as I could gather. It seemed like a very nice unit, with great features, and at a reasonable price. I contacted my avionics shop and told them to set up an appointment for me and order the hardware.
Now, the Garmin website states (check it out) that the suggested MSRP for the basic unit starts at $7495, which is what attracted me in the first place. Most good A/P’s are over $20K.
The shop calls back and tells me that the basic unit (2-axis) is $12,300 on the dealer’s price list. And that’s for the simplest (2-servo) unit.
Oh yeah..and Garmin tells him to expect at least 100 man-hours for the install, not including any time spent to remove the old gear. So that’s another $13,000.
Bottom line: we went from $7600 + installation to over $25,000. Talk about bait and switch…
Needless to say, I cancelled the order. I’ll just get my old STEC repaired for far less.

Administrator
Shoreham EGKA, United Kingdom

Off_Field wrote:

As I understand it no. The GFC500 gets the gps data from the G5. This can get the data from its inbuilt gps, an external gps antenna or a gps box like the 430 (w) 650 etc. I think this just gets one RS232 from a box.

Perhaps there is a way to do auto switching but I do not think it is common or standard.

According to the G5 installation manual, if there are dual GPS boxes, only one have the RS232 connection to the G5.

ESKC (Uppsala/Sundbro), Sweden

Peter wrote:

If the AP is wired to get GPS data from either GPS and auto-selects. Does the GFC500 have that capability?

As I understand it no. The GFC500 gets the gps data from the G5. This can get the data from its inbuilt gps, an external gps antenna or a gps box like the 430 (w) 650 etc. I think this just gets one RS232 from a box.

Perhaps there is a way to do auto switching but I do not think it is common or standard.

Both of my posts above are symptoms of a well-known industry-wide issue: the tendency to “engineer” flight systems, rather than “make systems that fly well”

From an engineering perspective, IAS mode is perfect, safe and optimal.

Just ask the pax how safe they feel during an IAS-CLB vs a VSI-CLB and you will no doubt get a different view…

It is not drones that we are flying, after all there are humans onboard…hence Peter’s PIT climb system is not that bad …

Antonio
LESB, Spain

Mooney_Driver wrote:

IAS mode will keep the IAS selected, which will gradually reduce pitch and subsequently vertical speed up to the point where the airplane will de facto level off

The issue with this mode is not the progressive pitch adjustment to maintain IAS as power is reduced, which always works great.

The issue is adjusting for minor shear and/or turbulence, where maintaining the set IAS requires quite heavy pitch (and accompanying G) excursions, depending on how accurate you want to be (system control gains in the IAS loop) . You can clearly see that in t he depicted video where pitch changes up and down 20 degrees to maintain IAS.

In airliners these pitch excursions bring pax (or even pilot) discomfort which is why a lot of times VSI mode is used instead.

Last Edited by Antonio at 13 Apr 13:47
Antonio
LESB, Spain

Yes it is a geometry thing. We discussed it briefly early on this thread:

NA you could typically climb at 3 degrees path at low altitude and perhaps 1 degree high up: a delta of 2 degrees.

Peter’s system is to fly same pitch 8degrees all the way up, so for example that is 5 deg AOA low down and 7 degrees high up, slowing down from say 120KIAS to 95 KIAS.

Even though it is not the most efficient it works fine due to the higher cooling requirements at 80% pwr low down vs 45% pwr higher up.

In summary: it is quite practical in his particular operation. And yes of course he can stall the airplane in attitude hold/pitch hold mode, just a matter of the right combination of pitch/power at that altitude

Antonio
LESB, Spain

It is just geometry,what ever the angle of attack is when the AI is at zero, for e.g. 4degrees plus the pitch attitude will be the new angle of attack when the pitch attitude is held constant and the flight path is level because the excess power is no longer excess.

E.g. 4 degrees plus 8 degree pitch attitude = 12 degree AOA which is often less than the stalling AOA.

If the power subsequently fails or is reduced then of course you will need a descent, and the numbers will be different.

If your descent angle is say 1 in 12 which is about 6 degrees, then you might get something like 6 (for the descent) + 4 (incidence) plus another 2 degrees pitch attitude to hold about 12 degrees AOA.

Of course flying at a different speed or config than the last example will vary the descent angle.

Last Edited by Ted at 13 Apr 11:04
Ted
United Kingdom
177 Posts
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