Autopilots in Turbulence

[Wiggums]

I've only flown with an autopilot a few times. I was wondering if autopilots do a good job of flying the aircraft in turbulence, or if a human can do a better job?

 

[AWACoff]

Pilots would say that they could fly it better. The people in back on the other hand would probably say the autopilot does a better job. The "soft-ride" mode that many autopilots have really do fly the aircraft more smoothly than human hands.

 

[skiddriver]

Also, as always, read the manufacturer's operating instructions. Most will tell you to disengage autopilot in significant turbulence. As you are probably aware, when it gets really rough, you're holding attitude vice altitude, which is not a mode most autopilots operate in.

If it's rough enough to slow to penetration speed, I punch off George and fly it myself.

 

[Airline Pilot27]

That is a good question and really depends on the type of turbulence that you encounter and the autopilot. Airline type autopilots are generally designed to maintain the aircraft on a certain LNAV and VNAV mode in all aircraft equipped with a flight director and are typically sophisticated enough not to overstress the airframe.
LNAV or Lateral Navigation mode programs a flight director to command one of several different modes depeding on what you have selected. They can be Heading (the aircraft flies the heading as shown by the heading bug), Vor (the aircraft turns to keep the CDI centered) etc.
VNAV or Vertical Navigation mode programs the flight director tp command other "vertical" modes such as Altitude Hold, Vertical Speed, Indicated Airspeed, and a Basic Pitch mode.
Whether or not the autopilot follows the flight Director depends on whether you have the Autopilot selected. As you can see the Autopilot follows those inputs and in some cases the autopilot takes other factors into consideration before it manipulates the flight controls. In the EMB 135/140/145 it is recommended that you allow the aircraft to fly the aircraft and set a thrust for Turbulence penetration. If the Autopilot is not performing to an acceptable level it can be deselected so long as the pilot does not chase airspeed/ altitude.

 

[dsaviation]

I'm with Skiddriver. RTFM, but if you are really in the goo, most likely you can do better by not chasing an altitude, rather an attitude.

Of course, some guys can just anticipate the bumps and put in a correction before anybody even feels it.

 

[Saluki Dawg]

AirlinePilot 27,

I've never had the autopilot perform at an acceptable level on any of the ERJ's, especially on an ILS. Embraer ought to ashamed of themselves trying to pass that thing off as an autopilot. I've had winglevelers in a Cessna 172 do a better job than that thing.

 

[Airline Pilot27]

Saluk Dawg,

"I've never had the autopilot perform at an acceptable level on any of the ERJ's, especially on an ILS. Embraer ought to ashamed of themselves trying to pass that thing off as an autopilot. I've had winglevelers in a Cessna 172 do a better job than that thing."

The autopilot on the ERJ is one of the worst that I have ever used. For a fifth generation aircraft it does have much to be desired. It is notoriously bad during Localizer/Glideslpope capture and corrections. However the autopilot seems to function quite well enroute especially when FMS equiped. And as far as turbulence is concerned our Operations Manual does recommend its use and I have not yet had a problem in this area.
As bad as the Auto is I think the ERJ's radar is even worse. The other day on a moonless night we penetrated a CB and found ourselves getting some Moderate/Severe. The Radar was functioning and properly set but did not pick up this CB for some reason. The Autopilot did a good job of flying the AC. I wish I could say the same for the RADAR.

 

[Wiggums]

How do you know when it's rough enough to slow to Va/Penetration Speed? What's the worst turbulence anyone has encountered in a light aircraft.

I've got some students that are scared of turbulence, especially at night, and I'm looking for some stuff to reassure them.

 

[TurboS7]

I was flying out of ANC on my way to SIT VFR in a PA-31-350. I was flying up Turnagain Arm heading for Portage Pass. Just as I rounded the bend we dropped 500 feet, my kids were literally on the ceiling as it was early morning and sleeping. I did a 180 and flew up Chicaloon Pass landed and got fuel at GKN. Then I climbed to 11,500 and flew on the SIT. The aircraft can handle way more than the averge person, when things start flying around the cocpit you are in moderate. Severe is loss of temp control and extreme is more than the above. A light aircraft can handle a lot of turbulence, tell your students to tighten their stomach muscles and enjoy it.

 

[AWACoff]

The worst turbulence anyone has ever experienced in a light aircraft was "Extreme". Some of those people are not around to talk about it today.
Extreme- Turbulence in which the aircraft is violently tossed about and is practically impossible to control. It may cause structural damage.

I would venture to guess that the type of turbulence that is worrying your students is "Moderate" at the very worst.
During moderate turbulence, Occupants feel definite strains against seatbelts or should straps. Unsecured objects are dislodged. To make them feel better about turbulence, show them in the POH how many Gs the aircraft is designed for. 4-6 Gs is a lot of stress (more than ANY rollercoaster) yet the aircraft is perfectly fine. On top of that, when the aircraft was designed, there was a safety cushion built into the design so should you inadvertently exceed the G rating of the aircraft (per the POH), the aircraft SHOULD not experience permanent deformation. Of course that is on a brand new airplane.

PS. I thought it was just Lakes E120s that had crappy autopilots. I'm not exactly happy to hear that they all are bad when trying to capture in approach mode.

 

[sabreliner]

Hmm...and I would have thought EMB would have put a better autopilot in the jet than the one we have in the E120. Guess the 145 really is just a Brasilia with jet engines.

Man that thing is horrible!! Guess that is what you get when you buy an airplane from a third world country at bargin basement prices!

 

[Saluki Dawg]

Unfortunately, you're right, it's pretty much a Brasilia with jet engines. Don't get me wrong, I think its a great flying little jet, but it does have a lot of little quirks.

AirlinePilot 27,
Don't even get me started about the Radar on that thing. That Radar has flown me into stuff that I would rather try and forget. I hate flying that thing to Mexico at night because the WX is awful and the Radar doesn't do the job. My eyes do a much better job at WX avoidance at least in this airplane.

 

[eriknorth]

This is a bit off subject, but speaking of autopilot functionality, the April edition of Flying Magazine has an article worth reading regarding autopilot and how it responds to failures. It's on page 14 under the heading "More Troubleshooting."

 

[328dude]

Im just curious for you ERJ guys. You guys have the Primus 1000 in that thing right? We run the 2000 Primus but I don't have any of the complaints I see here. I'm just curious if the 2000 is just that much better then the 1000.

Thing is always dead on it light to occasional moderate turb, and dead nuts on the ILS.

Any other Dork drivers have problems with what the ERJ guys and gals have?

 

[Drifter]

An old mechanic friend of mine (who's worked on everything from the little guys to the Majors) told me that he has never seen an airplane damaged from turbulance. Anybody actually done damage to their airplane from flying in turbulence? Tell us about it.