Discuss the problems and solutions to all of the situations that Pilot X finds himself in.
By Echo Delta
#1058763
The Price of Trinkets

David Phillips tells the tale of four friends, shopping for aviation goodies at a trade show, but they get more than they bargain for...

The day had been a success. Pilot X and his three flying compatriots had taken in a well organised and interesting aircraft trade show in the Home Counties. They had left their base early that morning having filled the tanks in the club’s new G1000-equipped C172. A check of the weather indicated a stationary high-pressure system holding to the right of their planned, southbound track with optimistic TAFs. The aircraft had performed well and completed the 250nm trip from Ireland, including the significant sea crossing, in precisely two hours. Throughout the flight, the pilots spent much of the time finding their way around the navigation features of the G1000 MFD.
Met by a fuel bowser on landing, Pilot X made a quick mental calculation and arranged for 50lt of expensive avgas to be added to the tanks. At this, he rushed off and joined his three friends who were already flexing their credit cards with enthusiastic anticipation.
Some six hours later the foursome returned to their aircraft, complete with various aviation trinkets that would undoubtedly make them far better pilots. Pilot X was looking forward to being in command on the return leg, especially since he now had a brand new ANR headset to try.
The four pilots completed a quick walkround, threw their purchases into the baggage compartment, strapped themselves in and started up. While taxying, Pilot X noted that the fuel gauges appeared to indicate less than he expected at just under 15usg a side, but he was sure they would be OK. They had departed this morning with about 170lt of fuel, flown for two hours and he had arranged a 50lt top-up. By his reckoning they must still have about 150lt for a trip that was only going to take two hours. Furthermore, he suspected that a rather tail-heavy attitude meant that the fuel gauges were giving an overly pessimistic reading.

Heavy beast
After a short delay Pilot X was cleared to depart and it was only during the take-off roll that he recognized the degraded performance of the aircraft. He was already aware that the new ‘glass’ C172 was a heavier beast than the more traditional models but he was genuinely surprised at the slow climb rate. Nevertheless, full throttle and a cruise climb of 90kt gave him a climb rate of 500fpm and an average groundspeed of 70kt. After about 15 minutes he levelled the aircraft at 6,500ft and allowed the aircraft to accelerate before finally retarding the throttle and changing frequency to the next ATC unit. ATC was busy and it took some time for Pilot X to get his call in before he finally had time to relax.
Switching on the autopilot and linking it to the GPS flight plan, Pilot X finally joined the animated conversation that was ensuing about the merits of high-wing over low-wing. After about half-an-hour, he completed a FREDA check and noted that the fuel gauges indicated 10usg each. He also mentally chastised himself for not leaning the engine after he had levelled off; he gave the mixture plunger a couple of anticlockwise turns. He again dismissed the low gauge reading as an anomaly due to the rearwards C of G but quietly ran through the day’s fuel calculation. No, he must be right.
Meanwhile the conversation had turned to the aircraft’s performance and ETA. It looked as if the homeward trip was going to take somewhat longer than the morning’s outbound and the pilots discussed the frosty reception they would all receive from their respective spouses. The GPS indicated they still had 160nm to go and just less than two hours flight time. Inevitably, the conversation focused on fuel and the continued inaccuracy of the GA fuel gauges, even on the most modern aircraft.
The pilots each revisited the figures given
by Pilot X and they all agreed that things were fine. Eventually, the most experienced pilot
broke the silence by suggesting that they consider their options in another 30 minutes. Pilot X accepted these wise words and continued towards destination.

Radio silence
Approaching the coast, Pilot X completed his coasting-out checks and recommenced the discussion about fuel. The gauges seemed to have settled around 10usg a side and the quorum decided to press on, there being only 85nm to go. After all, landing at the nearest GA airfield that was 15nm behind them would cost them more money and at least an hour. Some 10 minutes later, the G1000 PFD annunciator panel lit up with a ‘Low Fuel L’ indication. This was accompanied by an incessantly loud chiming noise that took Pilot X some time to silence. Not long afterwards, the chiming returned with an additional ‘Low Fuel R’ annunciation. Pilot X asked for the aircraft flight manual to be passed forward while he juggled with his ANR volume settings… only to be told that the manual was lost underneath a pile of trinkets in the baggage compartment.
By now there were no options − they had to continue towards their home airfield. The next 45 minutes were tense with each pilot continuously revisiting the fuel calculation. As the coast finally appeared, the friends started to relax but Pilot X chose to keep the aircraft high in case the engine started to cough.
Tuning in to the airfield’s frequency, Pilot X wasn’t surprised when he didn’t get a response at this time of the evening. He positioned the aircraft on a long final, completed his checks and reconfigured the aircraft for landing. At about 200ft he looked through the rapidly forming mist and could just make out the club’s Tiger Moth lining up at the far end of the runway. Aware that the old biplane didn’t have a radio, he was still surprised when the aircraft commenced a take-off roll. Pilot X had no option but to select full power, raise the drag flap and, conscious of his parlous fuel state, he commenced a climbing left turn with the intent of completing a tight, low-level circuit. For the umpteenth time the low fuel annunciator started to chime, together with a barely discernable background buzzing.
At 300ft he increased aileron input in order to keep the turn going, while noting that he still had two stages of flap. He quickly reached for the flap switch and raised the last two stages in one go. Some 10 minutes later the local fire brigade arrived at a smoking pile of twisted metal having been alerted by a dog walker.

Questions
1 Fuel planning is obviously an issue. How could a thorough knowledge of the G1000 system have helped?
2 The aircraft’s Flight Manual has some helpful information regarding performance and fuel burn. How relevant would that information have been in this circumstance?
3 What is the most likely cause of the crash?
#1058952
1. The pilot could have entered the fuel status into the G1000 at the start of the flight, when accurately full and updated it after refulelling. He would then have had continuous information about fuel remaining, range at the current fuel flow and fuel in the tanks at destination. The G1000 also gives fuel flow continuously. This would have alerted X to his failure to lean. He could have used the G1000 EGT feature to lean accurately. Also, as concern about fuel grew, he could have set power and leaned for greatest range.

2. The AFM information has only been partly useful as Pilot X did not lean in accordance with the manual, nor did he know accurately how much fuel he had on board. Nevertheless, with the help of the AFM, he could have set up the aircraft for best range, even though he didn't know how far he could fly. Over water, this would still have been a good strategy.

3. African Eage is right, I think -- the background buzzing was the stall-warner. Additionally, as the Tiger was taking off in the opposite direction to X's approach, the wind must be light and X could have made a tear-drop approach onto the Tiger's departure runway. This would have avoided the steep climbing turn and allowed him to remain within gliding range throughout, in case the engine quit.

Alan.
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By KNT754G
#1059404
Alan has got the vast majority of it (and AE with the stall)

The AFM would also provide details of best altitude for max endurance. of course this has to be offset against the headwind they were experiencing on the way home (the static high tells us it would be thus).

The G1000 is a wonderful tool and can tell you so much, but only if you know how to set it up and use it.
I flew one (G1000 C172) from Blackpool to Jersey and back mainly around FL70. we averaged just over 6 USG per hour.
By alanevans
#1059426
The AFM for a T206H (G1000) which I fly includes the use of 'lean-assist' procedure. This involves leaning steadily until the turbine inlet temperature peaks. The peak is held on the display. Then richen to achieve a TIT of 75 degrees F lower than peak -- i.e operating rich-of-peak. This typically gives a fuel flow of 20-21 usg/hour at 2400 rpm and 30 inches manifold pressure.

The Cessna Pilot Association recommends operation lean-of-peak if you have good engine monitoring (as provided by the G1000). When the CPA instructions are followed at the same engine power setting, the fuel flow is around 16.5 usg/hour -- about 20% less than as per the AFM. The power is slightly less, so the airspeed might be 1-2kt slower.

This procedure would have made an enormous difference to Pilot X's day. However, leaning this way is outside the scope of Cessna's and Lycomings operating instructions, but is practiced by many pilots.

I guess KNT's 6 usg/hour was achieved lean of peak, as the normal C172 consumption (F172P at 7000ft at about 70% power) is more like 7.5 or 8 usg/hour. Using AFM procedures for the F172P at 7000 ft, the throttle would be pulled back to about 53% power, much less than most pilots would normally use. Of course, KNT's aircraft must have been a later model than the P of about 1985 or so.

For sure, I agree that the G1000 is pretty fantastic, but does need time and work to learn its clever bits. There has been some work done in USA to show that there is little difference in the safety record betwen glass-equipped and conventional aircraft. This is hard to understand, unless it arises from using the G1000 features to push yourself into situations you would not normally venture to in dial aircraft and is made worse by inadequate training and familiarisation??? (I have only read the headline on this, not the detail).

Alan.

Alan.

Alan.
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By Gertie
#1060460
"They had left their base early that morning having filled the tanks in the club’s new G1000-equipped C172."

Four people in a G1000 C172 and full tanks? Surely they were overweight on initial take-off? Looks like an excessive desire to burn as much cheap fuel as possible and as little expensive fuel as possible leading to a whole string of errors.

Re fuel planning, whilst the G1000 does have some features not found in a clockwork aircraft these are a bit of a red herring. Proper calculation of fuel needed, proper leaning (on the way out as well as back), checking gauges, dipping the tank, all these things work just as well regardless of whether it's glass or steam, and would have resulted in success in this case.
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By tomshep
#1061188
Stationary high pressure system to the right of the outbound track. Tailwind out.
Headwind back, increased fuel burn.Refuelled, Pilot X had fifty five litres either side, not seventy five. They went out heavy and cruised at 125 KTs The burn outbound must have been 110 litres had the original 170 been a correct guess. If that is what it takes outbound, the return leg will take more than the 110 litres he had. Pilot X could have done it in his head.Too mean to brim the tanks so too lazy to dip them, despite not being fully conversant with the aircraft's systems. Although it is always highly desirable to understand the nuances of the equipment, sometimes this is an unrealistic expectation. In such a situation, dipping the tank is the perfect plan B. The failure to perform a physical check of the fuel level was the first error in the chain. Failing to heed the clockwork, even if it was not fully understood, the second. Complacency seems to have been the problem here or was it companionship? I just learned something. When flying with friends, tell them to get lost when you check the aircraft before flying. Keep your concentration.
By caber0
#1061681
I generally agree with what has been said already. I do think that the plane was overweight on the way out and possibly still overweight through most of the return flight, they had added some weight to the baggage area so the balance was probably out. By the time the fuel was exhausted the balance was probably distinctly tail heavy. Given this, on the go around the onset of stall would be pretty inevitable and recovery potentially not possible when the flaps were raised suddenly while already slow in a climbing turn. It is also possible that the pre landing checks had not been done so the engine was still leaned. It seems pretty typical that leaning is not covered in PPL training and SOP of club aircraft is to run full rich always to avoid risks of incorrect leaning to the engine. This would explain the failure to lean on the way out or early after the climb on the way back. The POH figures generally assume proper leaning so the calc for fuel used outbound would produce a lower burn than actually happened.
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By mo0g
#1061837
Wouldn't an aircraft's CofG being outside limits also affect fuel consumption?

I would suspect the CofG could well be aft of the limits, with all their "trinkets".
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By Gertie
#1062661
mo0g wrote:Wouldn't an aircraft's CofG being outside limits also affect fuel consumption?

I suspect that we were all assuming that without actually stating it out loud. I have no idea however whether the extra fuel burn would be tiny or highly significant.
By zlhglp
#1063174
The tail normally produces a downwards force, so if you have an aft CoG the tail needs to produce less lift, and there is therefore less induced drag and fuel consumption improves.

[edited for spellling]