Turbine Duke Condition Lever

[Sean Moloney]

Hi Rob. I couldnt find a support forum on the realair website so I will just ask this here. As you climb and the pressure differential reaches its max, the CABIN ALT warning light comes on even though my cabin altitude is still at 6000 feet. Now keep in mind I do not have any time in the duke but as for the beech king airs, 1900s is where I have a bunch if time. In these line of beech aircraft you do not get any indication of the cabin reaching the max differential. The pressure system has a built in relief that will not let you exceed the max diff. The only time you got a CABIN ALT master caution light was when the actual cabin altitude exceeded 10000 (for the Be10 anyway). Is this system simulated properly in the duke? Does the duke actually let you know you reached max diff on the cabin?Also it SEEMS the fuel vent heat is weird. On the king air the fuel vent heat did not affect the torque whatsoever. The ice inlet vanes did though. Maybe i gotta read up on the duke but usually beech is pretty standard. Can you confirm the fuel vent heat actually alters the engine torque?

Hi Jack,The Duke has a pressure differential indicator on the pressure gauge, it's the smaller needle. There were at least three different pressuriation systems installed into Dukes over the years so this is just one of the many. The red CABIN ALT annunciator lights when pressure differential reaches or exceeds the max allowable of 4.7psi. We do have a pressure relief valve simulated but we made a conscious decision to set it just over the 4.7 redline - it actually kicks in at 4.9psi. We could have made it kick in at 4.7psi, but we did it this way to force the user to manage the pressure differential to avoid over-pressurising the cabin. Being a simulator we wanted to make it so you actually need to use the pressurisation controls, otherwise they tend to be left alone to look after themselves. In real-life you'd be much more attentative of pressure differential because of its importance to your safety.Sean MoloneyRealAir Simulations

[Jack_C]

Hey Sean. I see what you are saying. I have about 4500 hours in the real king airs but none of them ever alerted you to nearing or exceeding the max differential which was 4.6 in the Be10 and if memory serves me it was 6.0 or 6.2 in the be20. Yes, they alerted you on the annunciator panel that the CABIN is exceeding a predefined cabin altitude but there was no panic if you set 20,000 feet on the pressure controller and you went above that (which would cause the differential to be at max) cause the cabin outflow valve and the dump valve would limit the differential automatically. It wouldn't harm anything in doing this. I was just curious if the real duke had an annunciator alerting the pilot to max differential since the king air 90 100,200, or the 1900 didn't have this.

[Sean Moloney]

Hey Sean. I see what you are saying. I have about 4500 hours in the real king airs but none of them ever alerted you to nearing or exceeding the max differential which was 4.6 in the Be10 and if memory serves me it was 6.0 or 6.2 in the be20. Yes, they alerted you on the annunciator panel that the CABIN is exceeding a predefined cabin altitude but there was no panic if you set 20,000 feet on the pressure controller and you went above that (which would cause the differential to be at max) cause the cabin outflow valve and the dump valve would limit the differential automatically. It wouldn't harm anything in doing this. I was just curious if the real duke had an annunciator alerting the pilot to max differential since the king air 90 100,200, or the 1900 didn't have this.

Hi Jack, yes that definitely makes sense to engineer the real thing to never exceed max pressure differential. There is a second annunciator light in our Turbine Duke that lights when you exceed 10,000ft cabin alt. It's amber and reads "CABIN ALT 10k".Sean.

[Superpilotv2]

Thanks Sean and the whole team for this incredible aircraft. BTW: Thanks for the info.

[Jack_C]

Hi Jack, yes that definitely makes sense to engineer the real thing to never exceed max pressure differential. There is a second annunciator light in our Turbine Duke that lights when you exceed 10,000ft cabin alt. It's amber and reads "CABIN ALT 10k".Sean.

Hey Sean. Just to touch on the pressurization. When you do hit max differential the cabin rate of climb on the gauge should then start to climb at the same rate as the aircraft VSI. In this, it keeps climbing at the selected rate on the controller.And in addition, I am at 24,000 right now and the CABIN ALTITUDE light is going off. On the Be10 we had a max pressure diff of 4.6 and we we able to JUST squeeze out 25000 and still not have a 10000 foot cabin. If the duke has a max diff of 4.7 then it should be able to cruise at 25000 without that CABIN ALT light coming on. Its on right now and like I said I am at 24000.

[zfehr]

Hey Sean. Just to touch on the pressurization. When you do hit max differential the cabin rate of climb on the gauge should then start to climb at the same rate as the aircraft VSI. In this, it keeps climbing at the selected rate on the controller.And in addition, I am at 24,000 right now and the CABIN ALTITUDE light is going off. On the Be10 we had a max pressure diff of 4.6 and we we able to JUST squeeze out 25000 and still not have a 10000 foot cabin. If the duke has a max diff of 4.7 then it should be able to cruise at 25000 without that CABIN ALT light coming on. Its on right now and like I said I am at 24000.

The cabin pressurization light will come on if you have an overpressure. This aircraft will climb fast enough you might have to adjust the rate of climb knob for the pressurization so you don't climb through any limits.

[bendead]

This aircraft will climb fast enough you might have to adjust the rate of climb knob for the pressurization so you don't climb through any limits.

Why this aircraft "original" never came with a pressurization adjuster linked on the actual vertical speed gauge ?Benjamin

[zfehr]

Why this aircraft "original" never came with a pressurization adjuster linked on the actual vertical speed gauge ?Benjamin

There is a pressurization rate controller knob next to the cabin altitude selector knob on the lower panel copilot's side. It is representative of the actual aircraft and is not linked to the actual vertical speed gauge.

[bendead]

There is a pressurization rate controller knob next to the cabin altitude selector knob on the lower panel copilot's side. It is representative of the actual aircraft and is not linked to the actual vertical speed gauge.

This pressurization rate controller knob is my problem.If i leave it alone the differential pressure will very quickly rise to 4-4.5 psi of cabin deferential pressure, not good for the aircraft structure, if I adjust it manually the passenger will be displease.Is there any "automatic system" that is possible to fit to the real plane to balance structural life and passenger comfort ?Benjamin

[zfehr]

This pressurization rate controller knob is my problem.If i leave it alone the differential pressure will very quickly rise to 4-4.5 psi of cabin deferential pressure, not good for the aircraft structure, if I adjust it manually the passenger will be displease.Is there any "automatic system" that is possible to fit to the real plane to balance structural life and passenger comfort ?Benjamin

The original aircraft was designed for a sub 2,000 fpm climb rate and probably 1,000 fpm or less into the higher teens. Most operations of the piston Duke would have been high teens and usually not over 23,000 feet hence the pressurization system that yields a 10,000 foot cabin at FL250. The added power of the turbines allow for a sustained climb rate unseen in most any piston aircraft. Therefore the default change value of 500 fpm for the pressurization system (this is arbitrary on the part of the programming, in the real aircraft this is set by the pilot and can vary depending on what you are doing) can put you in a situation where you outclimb the rate at which the pressurization can keep up. A sustained climb rate of 4,000 fpm for 4 minutes puts you at 16,000 feet from sea level and the pressurization will be attempting to be at 2,000 feet (something it cannot do). With that explained you also need to understand that the pressure change encountered while climbing (higher to lower pressure) is not the real comfort problem. You can sustain more than 1,000 fpm in a climb and still remain very comfortable, it is the descent where management becomes more critical for comfort. Once again the 500 fpm default setting is generally quite comfortable for the descent but 700 is almost an unnoticable difference for the ears. Approaching a 1,000 fpm descent and you will start the notice the change and anything more than 1,000 fpm descent can be quite uncomfortable. When flying unpressurized aircraft from the high teens/low twenties you can descend at about 1,200 fpm till about 10,000 feet, then you'll want to slow the descent rate for comfort. Pressurization frees you up from these descent comfort constraints and allows 2,000 fpm or higher descent rates to accomodate busy airport traffic areas and keep passengers and your ears comfortable.

[robert young]

'zfehr',Thank you. That is very well explained and is the reason why we mention in the Flying Guide that although the Duke will happily descend at a rapid rate, if you want to be accurate sim-wise, descent should be more sedate so the pressure differential doesn't get out of hand. Thanks for the explanation.Rob - RealAir

[bendead]

Zane thanks for your post, very informative and useful for future flight :biggrin:Last "maybe not" question. Is the original B60 structure strong enough to support massive "2k-3k VS" differential pressure ? I still have the old 4 engine Comet story in mind...Benjamin

[zfehr]

Zane thanks for your post, very informative and useful for future flight :biggrin:Last "maybe not" question. Is the original B60 structure strong enough to support massive "2k-3k VS" differential pressure ? I still have the old 4 engine Comet story in mind...Benjamin

More than strong enough. There is an STC in the works for the real aircraft to increase pressurization to probably 5.5 psi (for the turbine version) so that flights above FL250 could maintain a sub 10k foot cabin. The problem in the Comet wasn't as much the pressurization of the hull as the effect those pressurizations had on the window design that eventually fatigued and cracked.

[bendead]

Thank you Zane, you gave every informations i needed :smile:Benjamin

[bendead]

Operating cost of the B60T + The price of the duke + Turbine = close to the GDP of a small country :(Any idea if Realair can model turbines with vegetable oil or vodka ?Benjamin