TECHNIQUE
You need to take care of...
locations in the cockpit, all helping to lead to possible confusion in the heat of the moment. Another very significant change is that Cessna designed the 152 with only 30° of flap while all the other variants have 40°. Take something like the Piper Cherokee
range from the basic 140 through to the relatively complex Arrow — the flaps are mechanically operated and they all have a large hand-operated lever with a push- button lock that has a positive ratchet feel, visually very obvious and doesn’t need a gauge or indicator; it’s simple and relatively foolproof. Early Cessnas, some of which are still flying, had the same type of manual operation so why did Cessna change? Was it for the better? It would appear that incidents have
occurred with electric flaps that might well have not happened with good old manual flaps. That’s why I want to talk about Cessna flaps operated by an electric motor. Let’s look at some of the different flap
indicators first. The early 150s started with the indicator being a metal pointer moving along a scale situated above the pilot’s door. Then they repositioned it to be a vertical gauge, similar to the previous, but now down the left front door post; generally these are fairly accurate, maybe occasionally a bit glitchy but okay. Other Cessna variants have a flap indicator in an enclosed instrument case, usually on the right side of the panel, with a white needle that deflects up/down indicating the degree of deflection (00 - 400). This type of indicator is prone to ‘hanging’ and/or then ‘jumping’ so I generally recommend counting your flaps down, visually checking them, and glance at the indicator afterwards. Putting the flaps down takes approximately
12 CLUED UP Summer 2018
...how much flap
‘The most notable problem appears to arise with 150s and 152s’
2.5 seconds per 10° of flap, so count ‘one thousand, two thousand, stop’ per 10°, but be aware that the flaps come up a lot more quickly; 400 to 00 is about six seconds. More recent Cessnas have a pre-select
detent system, but this again varies from aircraft to aircraft so can still lead to misinterpretation or mis-setting. So how are the flaps selected? Looking at
the aircraft before detents were introduced, you have an up/down lever switch which, as a general rule, is spring-loaded while lowering the flaps so you have to hold the lever down to keep them moving; if you release the pressure the flaps stop. This makes it easy to put the flap down in stages when setting up an approach and particularly when using flaps during a PFL. But beware, the lever is not spring-loaded when moved to the flaps-up position and all the flap will retract in one go unless you manually stop them. This can be potentially very dangerous with any slow speed, low level operation, especially with full flap due to the sink that can occur as all the flap is retracted in one go, for example, on go-arounds, low airspeed/stall recoveries etc. (I say ‘as a general rule’ because I have flown a 172 where the flap lever was not spring-loaded in either direction, so you had to manually centre the lever when
Flap lever and separate indicator
lowering flap as well as when raising them). When it comes to the pre-select detent flaps confusion lies… some can have a detent every 100, some have a detent for just the first 100 and then you have to judge/guess the subsequent settings. Some indicate you can lower the first 100
at a speed higher than Vfe but must be back into the white arc on your ASI (i.e. below Vfe), for further flap. Look out for worn detents too; after a lot of use the detent can become a little rounded and the lever not stop where you intend it to. So you can start to see that simply
lowering and raising the flaps needs due consideration and awareness. This leads to what’s probably the biggest issue of all, the fact that the 152 only has a maximum of 30° flap whereas all the 150/172/182 models have 40° flap. The most notable problem appears to
arise with pilots who fly 150s and 152s. They look on them as being similar aeroplanes, but they most definitely aren’t. That extra 10° of flap on the 150 makes it very different which is why you need to be very conscious of which you are about to fly in. This difference has been attributed to be the cause of three fatal accidents in Cessna 150s in recent years. What happened? They had full flap (40°) down on take-off. With full 40° flap Cessnas would need a very long runway with no obstacles at the end just to get off the ground followed by a reluctant climb if you’re lucky; if fully loaded and it’s a hot day, there’s no chance. But how can a take-off happen with full 40° of flap?
THE CHECKLIST Most people have been taught to put the
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