Having the “climb-to-altitude” and vertical speed dialed in on takeoff, I was trained to hit the ALT and VS on the autopilot at the same time to hand over the climb to the autopilot once established in the climb. I’ve found that 50% of the time it must just register me hitting the ALT button because what ends up happening is that it ends up resetting my “climb-to-altitude” to the current altitude I’m at when hitting the two buttons. Basically, a very simple procedure seems like it has potentially disastrous results. When this quirk happens, I usually have to disengage the A/P to keep climbing and dial in the altitude again, etc. In VFR this usually doesn’t cause much of a problem, but in low IFR conditions in a busy environment I can see this would be a major distraction. Is there a better/more accurate way to get the results I want?
my understanding is that it is not hitting both at the exact time. you need to hold one in and hit the other … not in my plane right now (imagine that) - it is hard for me to remember which first but i believe it is hold VS in and hit ALT ( i may have it backwards )
give it a try and let me know pls
While training in a PFD equipped plane, I had the same problem and I had to fight the autopilot command to level off at the current altitude. I was told to press and hold VS in and then hit ALT. I also think this is the order as I don’t regularly fly PFD Cirri.
Dorian
Yes, as everyone is suggesting you have to press VS and hold it when pressing ALT.
The reason, as I understand it, is that it is of course impossible to press both buttons exactly at the same time…one of them will be a few jillionths of a second before the other (that’s the scientific term for it [:)]).
If you press just ALT you are telling the autopilot to hold the current altitude NOW.
If you press just VS you are telling the autopilot to capture the current vertical speed NOW.
So if you press both at the “almost same” time the FIRST one to get pressed causes the above behavior and the second one is ignored.
If you want the autopilot to use the preselector, the FIRST thing you want it to do is fly the selected vertical speed, so the sequence starts with VS, which you press and hold while you tap ALT. Both VS and ALT will display on the autopilot panel.
This works every time.
Tim
In reply to:
Having the “climb-to-altitude” and vertical speed dialed in on takeoff, I was trained to hit the ALT and VS on the autopilot at the same time to hand over the climb to the autopilot once established in the climb. I’ve found that 50% of the time it must just register me hitting the ALT button because what ends up happening is that it ends up resetting my “climb-to-altitude” to the current altitude I’m at when hitting the two buttons.
There is one other issue that MIGHT be happening besides how you are hitting your buttons. If your VS on the PFD is still showing a negative number (left over in memory from your last flight and descent before shutting down), hitting the VS/ALT combo will cause your VS to go to zero (instead of the 500 fpm climb you were expecting), and it will also reset your desired altitude to your current altitude.
For some reason, the VS on the PFD cannot go from a negative number to a positive number - it cannot pass zero. It also cannot go from positive to negative, but that has never posed a problem for my flying techniques.
There are several threads you can search for that will further describe this limitation.
Making sure your VS on the PFD is at zero or a positive number before takeoff (add it to your checklist) will solve things if this is what is actually happening.
Thanks all, I tried the method many of you mentioned holding the VS first and it wroked like a charm…uh…well after I remembered to set the correct alt and positive instead of negative VS just like SteveG mentioned. LOL
In reply to:
you need to hold one in and hit the other …
Stuart,
I think that’s the way I do it. It’s so reflexive now.
In reply to:
Stuart,
I think that’s the way I do it. It’s so reflexive now.
Andy,
Yes, it is.
This, and the use of ‘simultaneous’ HDG/NAV, often cause confusion.
In the Advanced Avionics course at the Cirrus Pilot Proficiency Program (CPPP), we teach two memory aids to remember the correct order for both.
[1] Always think OUTSIDE - IN. Keep the outside key pressed the outside key pressed in while you tap the inside key. So it’s HOLD HDG, then press NAV… and HOLD VS, then press ALT.
[2] What you’re doing tells you what to press. If you want to "Hold Heading to intercept a Nav course", then HOLD HDG, then press NAV; if you want to "Maintain this Vertical Speed until this Altitude", then HOLD VS, then press ALT.
In all cases, what is meant by “Hold X then press Y” is that you treat X as a Shift Key - keep it in until Y is pressed, then release both.
Whatever floats your boat.
This taste of the CPPP is brought to you by COPA. Hundreds of other tasty tidbits are available at the CPPP itself. [;)]
- Mike.
In reply to:
Andy,
Yes, it is.
This, and the use of ‘simultaneous’ HDG/NAV, often cause confusion.
In the Advanced Avionics course at CPPP, we teach two memory aids to remember the correct order for both.
[1] Always think OUTSIDE - IN. So it’s HOLD HDG, then press NAV… and HOLD VS, then press ALT
[2] What you’re doing tells you what to press. If you want to “Hold Heading to intercept a Nav course”, then HOLD HDG, then press NAV; if you want to “Maintain this Vertical Speed until this Altitude”, then HOLD VS, then press ALT
In all cases, what is meant by “Hold X then press Y” is that you treat X as a Shift Key - keep it in until Y is pressed, then release both.
Mike,
As usual, great information! I’m just surprised you had a picture of the Fifty Five X. [;)]
You know one little thing that works for me to reduce the chance of holding the current altitude when you want to climb is:
be sure that your Vertical Speed bug is set to a positive number; 650 works when you are not too high, but after 10,000 msl a lower number is better.
If the air is bouncy, and your fingers are walking, double check that you have a positive rate of climb after pressing VS then ALT and that the desired altitude is the one you dialed in; otherwise, the altitude you will be at is the one you were at when you pressed Alt without VS. When this happens, you know the sequence. make sure you have a positive number in the VS bug, redial your desired higher altitude, hit and hold VS, then ALT, then double check the PFD.
your surprised? don’t you realize before they delivered N1MR they had to “digitize” the plane for his records…
In reply to:
Mike,
As usual, great information! I’m just surprised you had a picture of the Fifty Five X.
Andy,
I didn’t… I found that one in one of the documents S-TEC publishes on the web! [:)]
- Mike.
In reply to:
your surprised? don’t you realize before they delivered N1MR they had to “digitize” the plane for his records…
Part by part…probably even down to the raw materials. [:D] A while back, I remember telling Mike to check his hard drive for a picture-folder marked “Bin Laden’s Current Hideout Location”
We joke, but Mike sure does come through every time one of us is searching for a photo to support or illustrate a post. [:)]
Now Mike,…I’m dissappointed, I thought you had taken a photo of EVERYTHING…
Great previous post however, when I first got my 20 I had similar isues with the autopilot. Now if I can just diagnose why after an hour or so in flight the autopilot (while on GPSS) suddenly wants to turn left. A disconnect and restart of the autopilot does no good, so I just have to go to HDG mode and follow the GPS manually (correcting for wind). It is bothersome. I am due an oil change in a couple hours and will have the SC look at it. Anyone else experience a similar problem?
Previous issues I have had with my autopilot have not re-occurred. I suspect some of them may have been operator error.[:)]
In reply to:
Andy,
I didn’t… I found that one in one of the documents S-TEC publishes on the web!
Mike,
You know what they say: If it flies, floats or…oops, wrong aphorism…If you don’t have it, know where to find it. [:)]
In reply to:
Now if I can just diagnose why after an hour or so in flight the autopilot (while on GPSS) suddenly wants to turn left. A disconnect and restart of the autopilot does no good, so I just have to go to HDG mode and follow the GPS manually (correcting for wind). It is bothersome. I am due an oil change in a couple hours and will have the SC look at it. Anyone else experience a similar problem?
Mine does EXACTLY the same thing. After fiddling with it a bit (and using heading mode), it will usually start working again. The problem is, it does it so infrequently it can’t be reproduced and thus cannot be diagnosed. Mine does it about once every 50 hours. It happened once during a CPPP with a CSIP instructor, so it’s not just me being crazy. If you learn anything, I sure would be interested!
Jim Knollenberg SR20 1281 N814
In reply to:
Mike,
You know what they say: If it flies, floats or…oops, wrong aphorism…If you don’t have it, know where to find it.
Andy,
I can think of one guy who can tie those two aphorisms together… Leroy Lockhorn.
[:)]
- Mike.
In reply to:
I can think of one guy who can tie those two aphorisms together… Leroy Lockhorn.
Mike,
Very good point. My mind amazingly didn’t even make the connection between the two–if it, um, floats, and you don’t have it, know where to find it. Maybe I’m maturing…yeah, right. Good ol’ Leroy Lockhorn. I grew up reading that one. Helped me early on figure out the kind of relationships I should run like heck from. [:)]