I have been told by several people that the Fairchild Metroliner is a quite difficult to handle aircraft. Aside from that, I have seen that it has suffered several accidents throughout its history. Does it have any aerodynamic deficiencies in its design or something like that?
Your question is basically asking for opinions. That said, I'll give you mine plus a bit of objective information. I flew SA-226 and SA-227 Metroliners for about two years, commuter flying (4 to 8 legs a day), mostly in U.S. Pacific Northwest weather, two pilots, no autopilot.
The Metroliner was considered by many to be a high workload, unforgiving aircraft. See this for more on that, but I did not find it unreasonably so. However, anytime you have a high work load, fast aircraft, the potential for incidents/accidents gets a little greater than if either of those things is not true.
It was not an airplane that you could get consistently good landings in if you consider a good landing one that is smooth (whatever that means). Clunkers greatly outnumbered greasers, at least for me. The tires were small and hard, and in my opinion the long landing gear magnified clunkers. You could increase your chances of a greaser by carrying a lot of power onto the runway, but that used a lot of runway.
Nose wheel steering was hydraulically actuated via the rudder pedals. It was not uncommon for the system to be inoperative, and the aircraft could be dispatched without it, in which case you had a castoring nose wheel. New captains dreaded being dispatched with inoperative nose wheel steering. Once you got used to it though, it was no problem. In fact, if you had to do some really fancy maneuvering on the ramp, you could turn off the nose wheel steering and if need be pivot about a main gear.
Far from any aerodynamic deficiency, at least in my opinion, it was great in that respect in that it was fast, but had the ability to slow down quickly. Controllers liked it (and took advantage of this) that it could fly at jetliner approach speeds from the outer marker inbound until short final. Controllers at SFO would often put us between jetliners going down final, or from a left downwind for 28L clear us from that downwind for an asap short final knowing that we could do it. We would touch down beyond where the jetliners did but still in time to make the turnoff to what was then the commuter ramp. When you dropped the gear and flaps and brought the props back to an almost flat pitch with no power, it quickly slowed and/or came down.
3$\begingroup$ How do you steer the aircraft during taxi without the nose wheel? Differential braking? $\endgroup$ Feb 12, 2017 at 21:08
2$\begingroup$ @HenningMakholm - (Guessing from the pictures) Possibly differential power between the two engines? If the propeller pitch allows reverse thrust, it could theoretically rotate around the center of mass? $\endgroup$ Feb 13, 2017 at 0:44
6$\begingroup$ @HenningMakholm Speaking for myself, whether in a Metro with the nose wheel steering inop or any aircraft with a freely castoring nose wheel, I used differential breaking for straight line tracking. In a turn,if it's a multi-engine aircraft, I typically used additional power on the engine to the outside of a turn to help it around, just as I would when operating a multi-engine aircraft with operative nose wheel steering if it was a sharp turn. $\endgroup$– TerryFeb 13, 2017 at 3:16
The data indicates that it is a challenging airplane relative to the Beech 1900, its closest competitor. Looking at hull loss events, or events in which the plane is destroyed beyond repair, here is what I see...
The Beech 1900 has had 41 hull losses since 1982, or 1.17 per year.
The Metro and Merlin IV (including the Merlin IV because it is often used in the same capacity as the Metro) have had 108 and 19 hull losses, respectively, for a combined total of 2.65 per year. That's over 2x the rate of the 1900.
Now, why that rate is >2x higher than the 1900 is another question. I don't think it's a design deficiency. The problem is the pilot. The Metro has been used in the freight business for some time which is a dark corner of the aviation industry known for playing a little fast and loose with the rules. Combine the lax attitude of the freight world with bargain basement maintenance and add a plane that is not quite as docile as airplanes that pilots had flown previously, like Navajos and Twin Cessnas, and you get a turboprop with a reputation! Keep in mind that freight operators will upgrade pilots from piston twins directly into the left seat of a Metro and send them off single pilot. That was my path. Was it dangerous? Probably. But, as the meme goes: did you die? No...and who says no to a free type rating and turbine PIC, right?
The Metro is challenging to fly and it does punish pilots who become complacent. It also yaws very aggressively during V1 cuts and it will roll over if the pilot is indecisive on the control inputs.
- A V1 cut requires an immediate and decisive response.
- The nose wheel steering will take the plane off the runway if used improperly. If the pilot lands with nose wheel steering
engaged and the rudder pedals cocked to one side, the nose
wheel will touch down and steer the plane off the runway before the
pilot figures out what happened. I know two pilots who have done
this and was #1 in trail of one of them. Popped out of the clouds on an ILS and there's a Metro off the side of the runway in the snow!
- The propellers do not have auto-feather. They use a system called negative torque sensing (NTS). NTS is a system that senses a scenario in which the airflow drives the engine via the propeller instead of the engine driving the propeller. The NTS says, "oh, the engine is not turning the propeller...the engine must have failed," and the propeller tries to feather. As it feathers, another system says, "no, not yet..." and drives the propeller back to low pitch. This feels like pulses to the pilot, about one per second. If NTS fails and an engine quits, the propeller will not try to feather and the plane will roll over very quickly.
- The fuel control unit on the engines used to be a problem. If the FCU failed, it would fail open and let fuel flow unmetered into the engine. This is a bad thing. There was at least one accident in which an FCU failed and allowed fuel to flow unchecked into the engine which caused to engine to produce a lot more power than it normally would. The asymmetrical thrust (one engine at 100% and the other at ~150%, for example) feels like a yawing motion. This yawing motion is an indicator of a failed engine, and normally the plane yaws towards the dead engine. Pilots would respond instinctively by identifying the failed engine (the one in the direction of the yaw) and shutting it down. In this case, the engine shut down would be the properly operating engine. The yawing motion was caused by unregulated fuel flow into the engine causing it to surge and produce more thrust than the other engine. Shortly thereafter, the engine with the failed FCU over-temped and/or over-torqued and destroyed itself. The pilot, having already shut down the good engine, could not restart the engine in time and crashed. If I recall, a pilot survived and relayed the chain of events to investigators who then looked into the FCU. Who knows how many fatal accidents occurred prior to this accident in which nobody though to look at an FCU that failed open?
For context, I flew the Metro single pilot in the Rockies and Western Plains for a couple years, also no autopilot (virtual high five, Terry). I've never actually seen a Metro with an IFR GPS or autopilot. Do they exist?
$\begingroup$ Do we have a NTS vs autofeather question on this Stack? I'm curious about the difference... $\endgroup$ Feb 12, 2017 at 6:03
3$\begingroup$ I can't find one. Basically, auto-feather will drive a propeller to a feathered position automatically. NTS uses a piezoelectric sensor on the shaft to detect when the prop is driving the engine (the "negative torque" part) and begins driving the prop to feather but "bumps" against the governor which causes the pulsing sensation as the prop is pushed back to low pitch. NTS requires the pilot to take the final step of actually commanding a stop/feather of the engine; it will not completely feather on its own and will pulse along all day until the pilot either adds power or feathers. $\endgroup$– acpilotFeb 12, 2017 at 6:17
1$\begingroup$ Great answer! Wish I could give more than only one upvote. $\endgroup$ Feb 12, 2017 at 12:03
4$\begingroup$ The statistics is somewhat unfair to the Metro, because while the production number is similar, it has about 10 more years in service. Good statistics would be normalised to total number of hours across the fleet, but ASN does not have that number and I don't know where to find it (at least approximately). $\endgroup$ Feb 12, 2017 at 12:36
1$\begingroup$ Also the statistics should filter out the accidents that where the cause had nothing to do with the aircraft itself (trying to land below minima is equally bad decision no matter what you fly), but that would have to be hand-counted as ASN does not seem to qualify this. Still, the difference is rather big and in a small sample I tried technical issues seemed to be well represented. $\endgroup$ Feb 12, 2017 at 12:39