Twin loss of control - UK

@ RobertL18C

Almost unbelievable that something created around 1560 has such a close relation to a situation happening today.

As to why have electrically operated flaps – it’s nice to just flip a little switch

But it’s faster to operate a paring brake style lever 8-)

Furthermore, having flown a C182 through africa whose alternator belt usually came off after 15 minutes and whose charge regulator stopped before 12V, you start to value being able to extend and retract flaps without electric power 8-)

While were waiting for more detail on the 310 crash, a few thoughts about flap systems….

The 310 has split flaps, similar to those of a DC-3. Not terribly effective in the “high lift” sense, but they’ll slow you down nicely. They are electrically powered, and cable actuated. very reliable. The Twin Comanche and Navajo have the bad reputation for asymmetry. This is because one flap is driven by the electric motor, and the second by a drive cable (like a tachometer cable, I’m told) which are less than ideally reliable. Therefore the drill is that flaps are extended and retracted in stages, so if you get asymmetry, its partial, and can be managed. I was suddenly told this sharply while doing this in a Twin Comanche, and setting full flaps all at once for stall tests: “we don’t do that in Twin Comanches – ever!”.

The parking brake style flaps are nice, though people did not like the long bar in the middle of the cockpit (and in the 150, it simply did not fit), so electric flaps were welcomed. Additional to this, there is a possible hazard with the sudden retraction through the full travel. Design requirements state that sudden flap position change cannot result in a loss of control, and with a 180 series Cessna in some cases, it could be close. If there is flap unreliability because of an electric unreliability, it’s worth having a look at the electrical problem.

Piper Aztec flaps are hydraulic. However, most Aztecs only have one engine driven hydraulic pump, so you have to know which engine, ‘cause if that one quits, you’ll have to pump them up (along with the gear) while you configure the plane for single engine climb out – it gets busy for a minute in the cockpit.

Furthermore, having flown a C182 through africa whose alternator belt usually came off after 15 minutes and whose charge regulator stopped before 12V, you start to value being able to extend and retract flaps without electric power 8-)

This is perhaps more an argument for not flying that plane rather than manual flaps…

One preflight item for me is checking equal flap position (viewed from about 5m in front of the prop) at the full flap setting. A duplicate inspection is a mainly UK thing; the mechanic must have been asleep.

Me too, and in the TB10 I had the incident in until aerodynamic loads were imposed the flaps were equal. In the air, one flap was effectively retracted a bit as the torque tube lifted up to touch the top surface of the wing.

Never got a full and proper explanation of what happened. I was young and daft and let them off the hook and didn’t file an MOR

Did they not put the screws back in?

Sometimes screws come loose by themselves… I had a scary moment when I collected “my” Citation Encore from a scheduled maintenance event this spring (and our aircraft are really well maintained!). It has two sections of flap on each wing and each section is operated by bellcranks and pushrods attached to both sides like in this drawing here (the closest Google image search could provide):

A mechanic from the maintenance company showed me that one of the bolts connecting the pushrod to the bellcrank of an outer flap section had fallen out, nowhere to be found. Which means the the flap was only connected at one side instead of both. Invisible during pre-flight inspections, the mechanism is inside the wing and only accessible after removing several inspection panels. Also we can not really move the flaps on the ground because they are operated hydraulically and hydraulics is only available with the engines running. But what it dangerous? I don’t know. Flaps are only moved one stage at a time and if an asymmetry is felt, you put them back to the last position. But still, during a low-level go around at low speed/poor control authority this would certainly not reduce the workload.

Twins are safe if you are properly trained. With that said, I owned a 310Q for four years and the 310 (as a make/model) can be a bit tricky. The Seneca is a puppy compared to the 310. The key is speed. I never operated from short runways so I could always make flaps up takeoffs and I would rapidly accelerate to Vyse + 20 asap. Approach was same idea…Vyse +20 until runway assured.