B767-300 and 300 ER
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Distraction; Troubleshooting
ATC Issue All Types; Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Other / Unknown
Flight Crew Overcame Equipment Problem
Aircraft; Procedure
So we had multiple strange events on cruise and descent. During cruise we noticed an execute light on the FMS. Neither of us was sure what the execute light was for and the Captain scrolled through the FMS pages to try to figure out what wasn't executed. We were in normal cruise as I recall and had recently stepped to FL 370. Somewhere through the scrolling of pages the plane went into continuous thrust mode and started slowing down to drift down speed. Neither of us executed the drift-down. Neither of us even attempted to get drift down speed and altitude during the short flight to ZZZ. So I was not the designated Flying Pilot for the flight but I had control at the time and overrode the auto-throttles to keep us at cruise speed while the Captain attempted to fix the FMS and get us back to Econ cruise speed. Nothing happened but we were told by maintenance after the flight that the aircraft had done something similar on a previous flight. Secondly; on the descent while on the VNAV path the Captain extended the speed brakes and we got an 'Unscheduled stab trim caution and an autopilot caution.' No one touched the electric or alternate trim and the autopilot stayed engaged. We did not notice any changes in the aircraft. When I was about to run the QRH the message went away and we continued and mentioned the situation to maintenance. And on the ATC side; not to be whining; but we did get the tight visual approach inside the final approach fix. The Captain went off automation as the glideslope would not have been able to be tracked on the AP. We started out high and then ended up low on the glideslope with a correction. We were able to make the 1000 foot stable gate on the glideslope just barely. However I am noting these things because it is my opinion that ATC needs to stop treating heavy Boeing 767s carrying cargo like we are CRJs capable of making aggressive last second maneuvers in the landing pattern. I realize that some of us more aggressive pilots can use skill to make things happen; but we should not have to. ATC needs to treat us like every other heavy; low maneuvering jet. This sort of situation could lead a less experienced pilot to make a mistake.For the drift-down situation; I felt we did a good job preventing the situation. No one freaked out or did anything radical and we corrected the problem. The unscheduled stab trim was handled without any major issues. However we are occasionally getting these strange cautions on the auto-flight system that pop up and then disappear. We shouldn't be getting them at all if the plane is not having any problems. It makes you have to decide whether you run a QRH or not and whether you need to write it up or not. It also creates a distraction and a feeling of distrust on the aircraft. This is not a good feeling; especially considering recent events. As to the visual approach; the Captain probably could have said 'no' to the tight vector to final. We were in a left downwind to base and I could not see the runway but our vector was inside the FAF. We probably should have said no to the super tight vector. Once again; we made it work but should not have had to fly a heavy cargo plane that aggressively.
TWO EVENTS:Ev. 1 - at cruise; 370. I had brought up the VNAV Crz (Vertical Navigation Cruise) page to look at the Econ speed. For some unexplained reason; VNAV commanded the thrust to CON (Continuous); and the speed to the EO (Engine Out) speed. The MCP altitude was set at 370; neither of us had made any change to the CDU. The thrust levers had to be prevented from retarding. Pushing the CRZ (Cruise) button on the TMSP (Thrust Mode Select Panel) did not work. Eventually; I had to delete the speed in the VNAV CRZ page; at which point the FMC caught up and VNAV went back to CRZ. AP and AT (Auto Throttle) were engaged all this time. No altitude or lateral deviations were observed. Ev. 2 - On the arrival into ZZZ; we descending 13;000; just coming up to [the next fix]; when ATC cleared us to descend 11000. I selected 11;000; hit the button on the MCP and to help the descent; started to deploy the speedbrakes. We were at 280 KIAS. The 'AutoPilot' and 'Unscheduled STAB TRIM' came on the EICAS for 1-2 seconds before disappearing. The AP did not disengage. No further incidents; no lateral nor vertical deviations were noted. We landed without further incident.This flight seemed to have a couple of glitches in the software in the FMC. It was really inexplicable that the thrust went to CON without either of us selecting any other mode; either from the TMSP or in the VNAV CRZ page. While it may be possible that one of us could have hit the EO prompt; we were pretty sure that did not happen. And in any case; the EXEC (Execute) light would have been high-lighted. Neither of us saw that. As for the Uncommanded STAB TRIM; it appears that the AP was trying to compensate for a pitch movement; but the aircraft was not pitching down at all; we were leveling at 13;000; on speed at 280 KIAS; 11;000 was selected and the MCP button depressed once. Only when I started to deploy the speedbrakes (gently I might add); then the messages appeared on the EICAS. I had my hands and feet on the flight controls already; so was ready to respond to any deviations. Fortunately; the messages extinguished; the AP and AT remained engaged; and nothing untoward occurred. These two events appeared to be aberrations; from what we noted. Perhaps the software need to be updated; fine-tuned.
B767-300 flight crew reported various anomalies with the FMS.