.

It is a weakness that systems are tied together in a way that is so unexpected that not only did the pilots not realize this, but the manufacturer and the FAA didn't either until it happened.

You say "just the nature of the machine", well, that "nature" was hidden from view.

It is not reasonable to have the STABILITY of the airplane depend on a NAVIGATION fault.

This is like having an engine flame out because VOR receiver is out. That's stupid.

Mike C.

.

The FAA says:

"ADDITIONALLY, DUE TO GPS INTERFERENCE IMPACTS POTENTIALLY AFFECTING EMBRAER PHENOM 300 AIRCRAFT FLIGHT STABILTY CONTROLS"

That's well more than a single person, it is a Federal agency.

Hence:

"FAA RECOMMENDS EMB PHENOM PILOTS AVOID THE ABOVE TESTING AREA AND CLOSELY MONITOR FLIGHT CONTROL SYSTEMS DUE TO POTENTIAL LOSS OF GPS SIGNAL."

The FAA is saying the issue is serious enough to recommend the aircraft avoid the entire area that could be affected by the testing.

"Ignore that man behind the curtain" isn't working. The FAA specifically named the Phenom 300 in GPS NOTAMs:

https://pilotweb.nas.faa.gov/PilotWeb/n ... e=DOMESTIC

If you do avoid all the NOTAMed places and times, the Phenom 300 is of much less use.

Mike C.

So Mike. They are right simply because of who they are?
Has this always been so?

This whole thing started last February when one autopilot clicked off in an area of no gps. I don't know if smooth air or not. For now while things are being looked into that slow down below .63M. Not a big deal at all.

The 300 relies on AHRS supplemented by GPS position to accurately drive the primary yaw damper servos to damp out dutch roll motions. Don't you also have the secondary YD, aka the boat rudder? Would you please explain to me the details of the primary and secondary YD, their workings and envelopes before and how his incident has changed things? Facts would be helpful.

And for the record now, you cannot ever complain that any "federal agency" has anything wrong or incorrect. No doubt I will see you going through several other threads amending your viewpoint.

The 300 is a great plane.

but that is exactly the question we were asking…

why is it that the basic attitude & heading output of the AHRS does not suffice to drive the yaw damper servo, and obviously that YD drops off-line when the GPS fed into the AHRS has a problem?..I do not think that the complete AHRS output goes south, just because the GPS feeding into it has a problem..so a GPS flag drops off the A/P and the YD, as I understand..?

is that so..?

maybe someone in the know can explain that to us..

that really seems to be a condition very unique to that Phenom 300..

and YD is flight controls…has nothing to do with navigation..or maybe better said, should have nothing to do with a navigation sensor, other than rate based info from a gyro or AHRS..whatever...

.

sorry, but I do not have any determined opinion, and that Phenom sure is a nice jet..

I really wanted to know, because, I may lack a lot of knowledge about that avionics architecture, but I thought it quite unusual...

Not an expected behavior. Not an intended behavior. Not a behavior that was apparently known during certification.


Here's what the FAA said happened:

EMBRAER HAS RECENTLY RECEIVED A REPORT OF GPS 1 AND 2 SIMULTANEOUS SIGNAL LOSS DURING FMS NAVIGATION IN CRUISE FLIGHT FOLLOWED BY A GPS HSI 1 AND 2 FAILURE INDICATION, ATTITUDE AND HEADING REFERENCE SYSTEM (AHRS) 1 AND 2 FAULT AND, AFTER A FEW MINUTES, A STALL WARNING PROTECTION SYSTEM (SWPS) FAULT, VENTRAL RUDDER FAIL, YAW DAMPER FAIL, AUTO PILOT FAIL, AND CAS MESSAGES ASSOCIATED WITH UNEXPECTED ROLLING AND YAWING OSCILLATIONS (DUTCH ROLL) AT HIGH AIRSPEEDS.

Loss of navigation, attitude, heading, stall warning, yaw damper, and autopilot, and with flight instability.

No big deal?


Here they are:

FAA mentions the Phenom 300 avoid areas of no GPS in every GPS NOTAM recently issued.

No other airplane is similarly named in GPS NOTAMs.

The FAA notice gives quite a long list of failures and consequences for the Phenom 300 if GPS is lost.

Mike C.

Then why aren't other aircraft types mentioned in recent GPS NOTAMs?


Not intentionally, but as we all know, safety issues do occur.

In this case, part of the lesson is how bugs like this escape detection during development, testing, and certification as system become ever more integrated and complex. Seemingly unrelated things are now part of the fault chain.


Currently, with a weakness. I imagine this can be fixed with a software update.

Mike C.

IFIFY

I sure am glad my hoopty Baron will fly with nothing but gas, needle, ball and airspeed. Got sectional and E6B will travel.

I have no opinion on whether the Phenom 300 is a "great plane" or not, although I think that only the passage of time can confer greatness. Bonanzas and Barons are great planes. They have proven themselves to be great over many decades. Seems to me that the Phenom 300 is kinda young to earn such a label, but it's nice that people like John Oaks are so enthusiastic about it.

But to have flight controls dependent on GPS for proper functioning doesn't seem like a such a great "feature" to me.

Clearly, somebody goofed.

People probably started off saying the same things when they started putting generators in airplanes.