Commercial Oral Questions
- Thread starter Alchemy
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Alchemy
Well-Known Member
I already passed today! but good questions.
1) 9000 AGL: due to certification requirement to perform an emergency descent and landing within 5 minutes (fire)
2) Hadn't thought about this too much but I presume it had to do with maintaining a minimum main rotor RPM with full down collective during autorotation, but according to the POH it's for weight and balance. I did a W&B for my ship with a 125 lb solo right seater and it's out of lateral CG if you just fuel up the aux (unlikely situation I know). Unfortunately I will never have this problem, thus my training ship is the R44 instead of R22.
3) To minimize the risk of mast bumping?
I'm sure there are better answers and am eager to hear them!
1) 9000 AGL: due to certification requirement to perform an emergency descent and landing within 5 minutes (fire)
2) Hadn't thought about this too much but I presume it had to do with maintaining a minimum main rotor RPM with full down collective during autorotation, but according to the POH it's for weight and balance. I did a W&B for my ship with a 125 lb solo right seater and it's out of lateral CG if you just fuel up the aux (unlikely situation I know). Unfortunately I will never have this problem, thus my training ship is the R44 instead of R22.
3) To minimize the risk of mast bumping?
I'm sure there are better answers and am eager to hear them!
1. correct.
2. yes, oddly enough. That bird can actually be too light to where it can’t build lost Nr in an auto. Crazy indeed.
3. true. How does that occur in that situation?
Alchemy
Well-Known Member
1. correct.
2. yes, oddly enough. That bird can actually be too light to where it can’t build lost Nr in an auto. Crazy indeed.
3. true. How does that occur in that situation?
Well - a poor attempt to explain:
Applying excessive forward cyclic prevents the the rotor mast (and the helicopter) from applying it's full weight to the rotor head at the teetering hinge. In the absence of full weight on the rotor head, tail rotor thrust no longer acts upon the main rotor and fuselage/mast in unison, but disproportionately moves the mast & ship in relation to the main rotor. However, because the tail rotor is above the ship's center of gravity, the ship rolls right (facilitated by the teetering hinge) instead of just sliding right. The rotor mast swivels to the left during this right roll due to the helicopter's suspension under the rotor at the teetering hinge, potentially contacting main rotors at the rubber boot of the blade grip. Main rotor flapping due to high speed dissymmetry of lift exacerbates the problem, as does the tail-high attitude at high speeds (thus the 60-70 KIAS turbulence penetration speed recommendation by Robco).
D
Deleted member 27505
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Why is there a 9000’ AGL max altitude for the R44?
Why IS there an R44? (Alternate answer: 'cause Robinsons are the B-MAXs of the helo world.)
What is the purpose of the minimum gross weight for an R44?
'Cause otherwise it does somersaults during auto rotation. [see A1]
Why are low-G cyclic pushover maneuvers prohibited?
A real helicopter is 10,000 parts flying in loose formation; A Robinson helicopter is 10,000 marching parts resembling the loose formation described by a real helicopter flying. [see A1]
(I'm secretly envious of you helo jocks and what you do. I'm too wimpy for that stuff.)
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Alchemy
Well-Known Member
Well, I wish I could say with any kind of authority how good a helicopter the R44 is, but alas I have no frame of reference since it is the only kind of ship I've ever flown. I will have to take my betters' word for it and agree that it is probably pretty bad.
Compared to a Cessna an R44 is a god damned Tie-Fighter though (well, as long as you don't push forward too hard on that t-bar cyclic). The R44 feels like flying with cheat codes unlocked; I'm guessing an Astar, MD500, EC130 or something is even 10x better than that, but alas I will probably never know.
I will say that I was impressed with the dispatch reliability of the R44. Not once did it have any sort of maintenance problem in the 70 hours I flew it so far. Granted, the flight school has about 5 mechanics working full time and a hangar full of Robinsons going through annuals or overhauls all the time, but we never even had any squawks at the end of our flights that I can remember.
Next step for me is to take the Robinson Factory course in Torrance. My flight school will allow me to rent the 44 if I do so.
Compared to a Cessna an R44 is a god damned Tie-Fighter though (well, as long as you don't push forward too hard on that t-bar cyclic). The R44 feels like flying with cheat codes unlocked; I'm guessing an Astar, MD500, EC130 or something is even 10x better than that, but alas I will probably never know.
I will say that I was impressed with the dispatch reliability of the R44. Not once did it have any sort of maintenance problem in the 70 hours I flew it so far. Granted, the flight school has about 5 mechanics working full time and a hangar full of Robinsons going through annuals or overhauls all the time, but we never even had any squawks at the end of our flights that I can remember.
Next step for me is to take the Robinson Factory course in Torrance. My flight school will allow me to rent the 44 if I do so.
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USMCmech
Well-Known Member
like you I have nothing to compare to but I think it’s a good ship for its mission. I don’t care for the T cyclic but it’s not a deal breaker.
My only serious gripe about the R44 is the engine. The IO-540 is a great power plant in the nose of a Cherokee 6 or Cirrus but when you stuff it in the belly of a helicopter you can just expect trouble. The squirrel cage fan keeps air over the cylinders but the rest of the engine just bakes.
I wouldn’t buy one for that reason alone.
My only serious gripe about the R44 is the engine. The IO-540 is a great power plant in the nose of a Cherokee 6 or Cirrus but when you stuff it in the belly of a helicopter you can just expect trouble. The squirrel cage fan keeps air over the cylinders but the rest of the engine just bakes.
I wouldn’t buy one for that reason alone.
Alchemy
Well-Known Member
Yeah, I was only flying the Raven 1 with the carb'd O-540 which is pretty massively derated to 225 HP takeoff/205 HP continuous in that helicopter. It's my understanding that motor can make 260 HP in other applications (granted I flew an O-540 in a R182 that was only rated to 235, another de-rated situiation iirc). Plus Alaska where it was usually ISA -20 to -30 C.
But, owning a 44 is way out of my budget and will be for a long time. The 2200/2400 overhaul combined with the maintenance costs are just too much sadly, for just about any airline employee I would think (barring some kind of partnership/leaseback money making situation to offset costs). I will have to be satisfied with renting one, despite the costs of quarterly checkouts (I think that might be a good idea in a robbie though).
z987k
Well-Known Member
Ya, the parallel valve 540's go up to 260hp when spun at 2700rpm and with 8.5:1 pistons. They more or less reduce one or both of those to derate the engine. 225/205 is the lowest I've ever heard of them being derated. Mine runs pretty cool at such a low power setting.
The VO-540 which I always thought was the helicopter engine spins faster and makes more power.(305)
Alchemy
Well-Known Member
Interesting. The R44 Raven 1 motor is listed as an O-540F1B5 variant which has a dry weight of 400 lbs according to textron. Maybe the ones in the R44 are further lightened. Mixture is a "don't touch" control except during before start and shut down. Carb heat stays on almost all the time until it gets below about -15 C OAT or above 30 C. I've heard some people say they might lean for max performance takeoffs above 5000 ft DA, but there is no EGT gauge.
It's de-rated for increased reliability, weight savings, and "more consistent performance across various altitudes" supposedly (idiot-proofing?). Takeoff power limit is determined from a chart prior to every takeoff. You can pull full power in an emergency though, obviously. Hard to really know how much performance you could get on a cold day at sea level if you did. I'm guessing a lot. Not sure of the implications for the tail rotor if you did. Other parts of the transmission system might be part of the reason for the de-rate as well.
It's de-rated for increased reliability, weight savings, and "more consistent performance across various altitudes" supposedly (idiot-proofing?). Takeoff power limit is determined from a chart prior to every takeoff. You can pull full power in an emergency though, obviously. Hard to really know how much performance you could get on a cold day at sea level if you did. I'm guessing a lot. Not sure of the implications for the tail rotor if you did. Other parts of the transmission system might be part of the reason for the de-rate as well.
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z987k
Well-Known Member
So they just de-rated via manifold pressure then? And count on the human to do so?
Looking up the F1B5 on lycoming's page, it's rated at 260HP at 2800rpm. It's got a different crankcase, different mags and different studs for engine mounts. So the 225/205 are airframe manufacturer limitations.
Alchemy
Well-Known Member
Yep. This is in the cockpit and POH. It's on the checklist to look at it before engine start (OAT gauge is required equipment, but how accurate is it if you just pulled your machine out of a heated hangar
). You're allowed to add an additional 1.5" to the limits with full carb heat on. There's a redline on the manifold pressure gauge at 26.3" but there are debates about whether it really has any meaning. So it's all on the pilot not to exceed the limits.
z987k
Well-Known Member
I'm sure your MAP gauge read's in .1 in Hg increments, the lines are large enough and the needle steady enough to actually set that.Yep. This is in the cockpit and POH. It's on the checklist to look at it before engine start (OAT gauge is required equipment, but how accurate is it if you just pulled your machine out of a heated hangar
Alchemy
Well-Known Member
True, I just round down to the nearest Inch generally. If I'm in a confined area max performance takeoff and feel like it might start to settle into vortex ring state, I pull the power I need to maintain a positive rate of climb before a sink rate develops (hopefully the OGE hover chart prevents you from needing to exceed takeoff power, but I'd much rather exceed than get vortex ring obviously).
if confined so much that moving the helo 5 feet in any direction to exit the vortices isn’t possible, then that’s a heck of a tight spot.
Even if a sink rate develops in a max performance confined space, so long as you can maintain a controlled settle at 300fpm or less, it should still be manageable to at least make a controlled descent back to a landing straight down.
if the lateral room for in-place turning exists and you’re getting close to pulling max power and vertical climb rate is slowing, you can always reduce your antitorque (reduce left pedal) and thus reduce the power having to go to the TR a bit. The fuselage will rotate in the torque direction commensurate with the amount of antitorque you release, but you can gain a bit of performance to clear an obstacle and get moving past ETL.
badtransam97
Well-Known Member
I agree, I would pick another LZ if the area is soo confined I couldnt move 5ft any direction. My shop requires at least 1/3 rotor disc distance for LZ area.
On a side note, I know I dont post on here often, but I am happy to try and answer any rotor questions anyone has. I know @MikeD and a few others are helo guys and more active on here than myself, but I'm happy to help as well. Currently back in HEMS, from flying 767's at Atlas but hoping to go back to 121 pax after the corona scare settles down
On a side note, I know I dont post on here often, but I am happy to try and answer any rotor questions anyone has. I know @MikeD and a few others are helo guys and more active on here than myself, but I'm happy to help as well. Currently back in HEMS, from flying 767's at Atlas but hoping to go back to 121 pax after the corona scare settles down
I agree, I would pick another LZ if the area is soo confined I couldnt move 5ft any direction. My shop requires at least 1/3 rotor disc distance for LZ area.
On a side note, I know I dont post on here often, but I am happy to try and answer any rotor questions anyone has. I know @MikeD and a few others are helo guys and more active on here than myself, but I'm happy to help as well. Currently back in HEMS, from flying 767's at Atlas but hoping to go back to 121 pax after the corona scare settles down
Your input and knowledge is very welcomed and appreciated! We few rotor people, or even dual qual people, have to stick together around here!
Low_Level_Hell
Well-Known Member
The R22/44 scares me. Low inertia rotor systems and single engines shouldn't go together. Even with 4000 RW hours I wouldn't trust my reaction time to respond to an engine failure in the R22. Also what's up with the teetering flight controls? Does the instructor just get used to flying with his/her hand up in the air at a weird angle?
badtransam97
Well-Known Member
I would agree with you on the R22, I’m not a huge fan. The R44 and R66 on the other hand auto very nicely and almost JetRanger like...notice I said “almost” haha!
As far as the teetering controls, I have heard it was Franks idea to be cheaper, by having one cyclic control up through the floor, but mostly for ease of getting in and out.
I found I adapted fairly easy to resting my elbow on my thigh and my hand following on the controls with the student. Sometimes I could even fly without resting my hand on anything, if the student was about to crater us haha!
