Induction Icing and Fuel Selection and other annomalies

[Highiron 21]

After having this aircraft for some time, I'm finally starting to spend some serious hours with this light twin.

 

I have done periodic flights with it, but just by chance, usually in warm weather. I recently conducted some flights around my area in Canada and with the REX+Overdrive weather engine injecting real time weather I can honestly say things have been rather "cold" to say the least. -20C temps on the ground and below -30C up at altitude. During my flights, I have been experiencing complete eventual power loss. With the cold temps and presence of cloud, I knew this was an engine icing condition. Having flown many fuel injected engines in the real world, I found this rather unusual because it is quite rare and requires very specific conditions to occur. None the less, the engines were icing up. As per the Normal and Emergencies Procedures manual supplied along with the files it states that in the event of induction icing to pull the alternate air knob to the first indent to the cold alternate air position. These are the aluminum left/right engine alternate air knobs below the cowl flap knobs. It then further concludes that if the alternate cold air position ices up to pull the knobs all the way out to the heated position. Within Carenado's aircraft the knobs are non-functioning in the cockpit. The only solution I found to this problem is to use the "H" key on the keyboard set default to "carburetor heat" unless it has been re-assigned. This instantly clears the problem, but mucks around with the switch positions of several heat controls, such as the pitot heat and static port and probe heat. Using the "H" key also illuminates the "SURF HEAT" light on the annunciator panel that remains lit regardless of the surface heat switch position on the side panel. Oddly this light never comes on with the movement of this switch. Since the engines do fail due to induction icing, it would be nice if this was corrected with proper 2 indent positions as per the manual on the engine alternate air selectors. It would also prevent inadvertent re-positioning of the pitot heat switch with use of the "H" key, (I lost airspeed indications on several occasions because of this).

 

Selection of fuel tanks is also cumbersome. Currently the only way to move them is to cycle them through all their positions, including the "OFF" positions. It would be preferred to move them clockwise and counter clockwise through the mouse scroll wheel, or alternately creating click spots to move the selector directly to the desired position. Currently the only method of switching from AUX tanks to MAINS is to move through the OFF position which instantly starves the engines of fuel. In reality, one would have anywhere from 5 to 10 seconds before any indication of power loss.

 

Flaps only have 0, 22, and 45 positions. All examples I have seen have 0, 15, 30, and 45. The airframe used by Cessna is fairly consistent through 300 and 400 series aircraft and all examples I can find have the four positions including the 414 which I have experience with. Perhaps your reference aircraft is rare or was modified with a Robertson STOL kit?

 

Post lights illuminating the autopilot and cowl flap knobs is completely absent. Use of the autopilot and Yaw damper switch is extremely difficult when flying at night. The whole portion of the lower center pedestal is dark. Two post lights illuminate the autopilot controller and yaw damper switch and one post light illuminates the cowl flap and alternate air knobs.

 

Fuel burn values are way above those in the performance charts of the flight manual provided. Best lean value I could achieve was 44.7 GPH (295 Lbs/Hr) burn at 16,000 ft at 28" Hg manifold pressure and 2300 RPM with a temp of 6F below standard, that's over 60% of published values. As stated by others, the EGT gauge is of no use for leaning. I leaned until I could hear the engine drop in output then en-richened for normal operation. This is no where close to proper or normal procedure. The mixture should be leaned to peak EGT for optimal performance/fuel burn, leaned further for a 25F - 50F drop of peak EGT for maximum endurance at risk of shortening engine life span. Even with the lack of EGT values, an acceptable lean can be achieved by leaning until a drop of manifold pressure is noted, then en-richening to bring MP back to pre-drop value. Not sure if this is an issue with FSX/Prepar3D or not. Sound levels would not change as leaning too much would cause a drop in engine RPM, but the propeller governor would move the blade pitch finer to maintain engine RPM, resulting in no RPM sound level change what so ever. The only instruments that can be used for leaning indications is the EGT and MP gauges. Not sure how this one got past the real world users. According to the performance charts, the aircraft should have a range of over 1,200 NM @ 15,000 ft, I barely achieved over 600 NM @ 16,000 ft with leaning that was on the verge of destroying an engine in the real world. True airspeed was on par for the altitude, temperature, and power settings used so fuel consumption is defintely inaccurate. Currently the 340 is a pig on fuel.

 

Autopilot approach mode flys the aircraft 1/2 a degree above glideslope. Normal capture was made from below. Nose down trim began at glide slope interception. Instrument indications placed the aircraft constantly above the glideslope and remained a stable 1/2 degree above and never achieved re-capture. PAPI indications on the runway confirmed a above glideslope, high approach condition.

 

Electrical load has no effect on ammeter. This may seem of little concern, but in fact is very much a managed system in flight. With all the avionics load, landing lights, fuel pumps, and all the de-ice systems energized, it is very likely for one to see a "Low Volt" warning on the annunicator panel if engines are pulled down too low a RPM during an approach. So real is this issue that many times I have had to carry extra power on a approach to ensure the alternators are turning fast enough to carry the heavy electrical load of all the systems or risk quickly exhausting the battery causing possible instrument failure due to an undervolt condition. Very bad when conducting an ILS approach in IMC conditions with icing. In such conditions, flickering of the "Low Volt" light is common with activation of the electric hydraulic pump with gear extension. Currently, I can turn everything on and pull the power to full idle with no concern or consequence, a very unlikely scenario, especially with electric propeller heating elements. It's these things that make flying such multi engined aircraft more challenging and rewarding and thus more enjoyable in my opinion. Without these things the sense of achievment of flying these more demanding aircraft is greatly diminished, undermining the complex multi experience.

 

Lesser non performance issues I see are items such as the lettering around the left side fuel cap on the engine nacell being "mirrored". At night, multiple warning lights on the panel and warning annunciator illuminate and/or are completely legible. A bit of a "yuck" factor on this. The digital temperture readout on the clock and the O.A.T. temperature gauge above it are not even close in agreement in flight. I also agree with other postings that the clock should have the timer function working. It's vital when conducting non-precision approaches to determine the M.A.P. (missed approach point) and initiate the go around. In an aircraft such as the 340 or it cousins, the clock or ADF timer function would be utilized.

 

I hope this is seen as constructive input on the Cessna 340 product. I'm not trying to nit-pick, just make suggestions on polishing what is already a very fine product. I understand that the aircraft was released several years ago but provide these findings in the event there is a revisit to update the product to Carenado's improving standards, I believe it is certainly worthy and deserving of it. Overall I would like to emphisize, within the FDE limits of FSX/Prepar3D (and there are many with regards to constant speed props), there is more right with the product than wrong. My motivations are simply wanting others to experience the true joy these aircraft are to fly, as I have enjoyed them in reality.

[cvearl 60]

Its great when pilots with time in type provide constructive input. This was a great read! Thanks for that. I love flying this machine. It's a great model. I hope they can make these additional changes.

 

Can you tell me something? I have been studying this plane n the web and in footage. The POH says 2450 RPM and 28 inches mp is cruise yet I see footage and discussions of 30 inches in high cruise.

 

You have some hours in type. What did you typically true out at?

 

C.

[Highiron 21]

cvearl,

 

Sorry to see your question so late. Almost a year!

 

For some reason the post did not show any new replies (not bolded). I know AVSIM has had problems with their site over the year.

 

I was going to give a long winded answer to your question, but I see in another thread that you saved me the time. TAS is tied to temperature and pressure altitude so TAS will vary greatly as you had discovered yourself. Any power setting can be used for cruise within the green band so using 30" of MP is allowed, however fuel burn to TAS gain is not that great. When determining optimum cruise power settings we generally look for the point where increasing MP no longer gives us a efficient increase in TAS for a given Pressure Altitude. For example if each 1" of MP increase yields a 5 Kts increase in TAS from a specific benchmark, we look for the point where there is a significantly less increase in TAS for that 1" MP increase such as increasing a further 1" of MP now only increases the TAS by 3 Kts. We would use the last power setting where the gains were the most. Of course some pilots just want to go as fast as possible regardless of the efficiency, so they will use much higher MP settings, regardless of excessive fuel burn for little airspeed gain. In certain cases where range is also not the issue this can also be done. Also running higher MP settings with lower RPM's is much harder on the engine and can reduce it's life. Its really all about personal choice and discipline on how one operates their aircraft.

[flycaptjon 2]

Cverl, please refer to my post in this C340 forum under  'Cessna C340 Fuel System and Procedures'. 

 

I have several hundred hours in a real world Cessna C340A with the RAM IV upgrade to 325hp TSIO-520NB engines.

 

In the post mentioned above I have detailed the fuel management procedures, the power settings data for Cruise Climb 82%, Cruise 75%, 65% and 55%.

 

I had to modify the Carenado config file quite a bit to be realistic. I have also filed bug reports on their support site for the bugs in flap settings and a couple of other issues as Highiron had also pointed out.

 

Overall a great airplane, but I'm not sure the basis of the technical data they used for the design spec. I have a set of operating and service manuals for the C340 and while they miss some key specs. The flap settings on most C310s are 15/45 for the early models A thru H, and 15/35 for I thru the R models. The C340 and most piston 400 family are 15/30/45, except for the 404 and the turbo prop 425, 441.

 

Cheers,

 

Jon

[Robk182 0]

 

 

I had to modify the Carenado config file quite a bit to be realistic.

 

Can help me with these modifications on the config file please....?

 

Redgars from Venezuela

Robert Bernard