Discuss the problems and solutions to all of the situations that Pilot X finds himself in.
By Echo Delta
#1098886
Bushed Pilot

Hour-building, work pressures, knowledge of the aircraft, weight, altitude, heat… just where did this month’s Pilot X go wrong? Richard Boswell takes us bush flying

Pilot X wiped the sweat from his brow. In his short time bush flying, he’d learnt that in the heat and humidity of an African summer, trying to keep cool while loading the bags was a constant battle. He’d vowed never again to complain about the weather back home.
With 500 hours logged, he was gaining confidence. He couldn’t remember the last time he’d had a day off, but he didn’t care. Each day was a new adventure and more precious hours
in his logbook. 1,000 was the magic figure and
at the rate he was accruing them in the Cessna 206, he would have those within the next five months. After that, conversion onto the Cessna Caravan beckoned along with the valuable turboprop time he craved.
Today’s flight was another charter, carrying four adults to a remote bush strip. He’d filled the tanks before meeting the passengers and was pleased to see that they didn’t have an excessive amount of baggage. He loaded it all in the belly-pod, wiped the sweat from his brow again and briefed his passengers on safety.
It was two couples holidaying together, so he asked the slightly more rotund pair to occupy the centre seats. His training captain had been flying the 206 in the bush for 20 years and had informed him that on this turbocharged version, if you could see out of the window you would be in weight limit and if the tail of the aircraft was clear of the ground with everyone loaded you would be within C of G limits.
With his passengers and their baggage loaded, the aircraft tail remained clear of the tarmac, just. Deep down he realised that he was probably a few pounds overweight, but he didn’t really see what options he had. His destination was two hours flying away with no fuel on site. He could have told his boss that the flight could not be completed as he was a few pounds overweight, but that didn’t seem a smart career move when this aircraft had been doing this sort of thing for the last 30 years without incident.

Passengers asleep
Apart from the long take-off run, the outbound flight seemed uneventful. The GPS led him straight to the strip, a scar in the bush next to the upmarket safari lodge. He flew over the strip to ensure that it was free of animals and planned the approach; he couldn’t be exactly sure how long the strip was but he estimated at least 1,000m. This should be more than enough, even though he estimated the density altitude to be at around 4,500ft. Once again, he remembered being told that as long as you had 1,500ft you were fine in the Cessna 206 — he reckoned he had about double that.
He turned around to brief his passengers but they were all fast asleep, leaning against the side of the aircraft. Most of the flight had been conducted at 13,000ft and X was used to passengers quickly falling asleep. He had struggled to stay awake himself on occasions but felt that his body was slowly becoming acclimatised to altitude.
Turning downwind, he checked the Ts & Ps and selected the first stage of flap. He instinctively moved the trim wheel as he moved the flap lever, but he failed to notice the aircraft start to descend. It wasn’t until he got to the end of the downwind leg, reduced the power and selected the next stage of flap that he realised that the flaps were not deploying. His attention was now divided between flying the aircraft and trying to resolve the problem with the flaps...
Fly the aircraft, that was the main thing now. He didn’t want to get distracted by the emergency and lose control of the aircraft. He had the presence of mind to keep the speed up as he turned finals. But now it was decision time, continue the approach or go-around and try and sort the problem out? He ran his hand along the circuit breakers to see if any had popped; they were all in place. He moved the flap selector lever up and down but still no response from the flaps. 500ft above the strip he glanced round at his passengers. Behind him one passenger had woken up and looked at him with blurry eyes. Her husband remained fast asleep slumped against the door. X made the decision to continue the approach and make a flapless landing. Going around now would only alarm his passengers and he didn’t know what he would tell them. He kept the speed up and concentrated on the landing.
Across the threshold of the strip, X realised he was a little high but felt committed. It felt
fast, very fast, but he remembered that from when he had practised this some six months before. He planted the aircraft down hard so that he could get on the brakes. The Cessna contacted the bumpy surface and bounced into the air again. He had the presence of mind not push the nose forward as he pulled the power and held the attitude.
The aircraft hit the ground and bounced again. By the time that all three wheels were on the ground and X started braking he knew that he no longer had enough space left to go around or to stop before the end of the runway.
The aircraft skidded into the drainage ditch, breaking the nosewheel off and coming to rest upright with the propeller tearing holes in the
dirt. Just before he turned the electrical master switch off, with all the passengers sat bolt upright in their seats, he heard the distinctive sound of the flaps deploying.

Questions
1 What effect does have destiny altitude have on the landing distance required?
2 What prevented the flaps from deploying?
3 How well do you know the systems on the aircraft that you fly?
By pb6797
#1099175
Well, no-one else seems to want to have a go so :

1) Increased distance as your Ground Speed is higher for the same IAS. 3% per 1000 feet increase in altitude. He was also heavy and it was hot, so a triple whammy. Plus it sounds like he was hypoxic so reactions were dulled too.
2) Cargo door opening disables the flaps apparently. So that passenger leaning against the door probably put enough pressure on the microswitch to put it in "door open = disable flap" mode.
3) I only fly simple aircraft so I don't think they count as having "systems". If the flaps don't deploy it means either they or the lever has fallen off :-)
User avatar
By Gertie
#1099192
pb6797 wrote:2) Cargo door opening disables the flaps apparently. So that passenger leaning against the door probably put enough pressure on the microswitch to put it in "door open = disable flap" mode.

In which case the correct option - go around and sort out the problem in the air (maybe the flaps can be fixed, but if not at least you can get the flapless approach speed right the second time) - would have woken up the passengers (which is what he was afraid of) and automagically fixed the flaps!

On our honeymoon we went for a joyride, and heard in due course that a few weeks later one of the pilots at that outfit (a student on a summer job, something like that) hadn't wanted to **** off his (rich, powerful) passengers by turning back or refusing to fly them in marginal weather, and had flown into a mountain: all dead.

(I woke up and surprised a passenger with a go-around once. The other passenger was slightly more with it, and was expecting me to go around from the screwed-up approach, and said he'd been wondering why I was leaving the decision so late!)
By alanevans
#1099222
1. Effect of density altitude on the landing distance required
A high density altitude means low air density. This means that the aircraft flies at a higher true airspeed to achieve the same indicated airspeed. This means the touchdown groundspeed at high density altitude is higher than at an airport at ISA conditions, and the result is a longer ground roll. For the T206H at maximum weight, the landing roll is 18% longer at 4500ft density altitude compared to ISA and the landing distance is 13% longer.

In the case of a flaps-up landing the approach speed is increased by 9kt and this increases the landing distance and landing roll by 45% (again for T206H).

So, even if Pilot X correctly flew the short-field flaps-up approach speed (which seems doubtful), the landing roll would be 170% longer than a full-flap landing at ISA and the landing distance would be 163%. Add another 40% of the ground roll for the dry grass runway and the landing roll for a well flown approach is 620m. Add the normal factor of 1.4 and you have 866m.

Now add all the factors together: density altitude, no flaps, fast on approach due to lack of preparation and distraction, high over the threshold, plus failure to land properly, maybe compounded by hypoxia as pb has said, and you can see why he went off the end of the runway.

2. What prevented the flaps from deploying?
The 206 has a large door for luggage and for the rear passengers, much larger than, say, a C172. If the flaps were lowered on the ground with this door open, the flaps would hit the door. So a switch is fitted to the door, preventing the electrical flaps from operating if the door is open. On the accident aircraft, likely a combination of improperly adjusted switch and the weight of a passenger leaning on the door caused the 'door open' switch to operate, preventing flap deployment.

Preparing the passengers for landing would have solved the flap problem.

3. How well do you know the systems?
Far from perfectly. The T206H, which I sometimes fly, has the large Cessna POH, a large Garmin G1000 manual and smaller manuals for autopilot and tip tanks. The trick is to know what is in these manuals, so if you have a problem in flight, you know where in the emergency checklist or in the manuals to find the answer to the problem. This is not much of an excuse for pilot X, though, as the flap/door switch is clearly mentioned in the walk-round section of the POH (at least for modern aircraft).

Alan.
By -DV8R-
#1107561
I just wanted to say I'm impressed with the clever answers, and point out a great typo:

question 1 is about "DESTINY" altitude

Considering the confusion about thinner air, amient temperature effects, I find this a very fascinating and befitting tyop... oops typo !!

Happy landings,
D
User avatar
By Moose
#1152575
An interesting and very relevant little incident.

1) Increased LDR. A wrote a small article on DA here: http://indopilot.blogspot.com/2013/01/d ... itude.html

2) Dunno, never flown a 206. With the Porter we can fly along with the slide doors open.

3) Never enough! The original PC-6 AFM was pretty dire and had very little information in it. Thankfully with the newer G950 glass cockpit version the AFM is a lot better with excellent diagrams and explanations. I know a pretty decent amount about my aircraft but am always learning more by chatting to more experienced drivers.