Jaybird180
Final Approach
C-172S has one
Aviation and Flying Questions That You Have Been Dying To Ask And Want To Know
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C-172S has one
poadeleted20
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There may be a single feed tank downstream of the valve on gravity-feed planes like the C-172S Jaybird mentioned, or there may be separate sumps upstream of the selector like there are on the Grumman AA/AG-5-series inboard of and below the bottom of the fuel tanks, hidden in the "bumps" above the main landing gear.
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Dav8or
Final Approach
It's simple really.
That is how it used to be explained, but though the use of the scientific method, we now understand this to be true-
Dav8or
Final Approach
Well, if your airplane has more than one fuel tank and a left and right selector, you do have a reserve tank. Some people employ a strategy on long distance, fuel critical flights where they will run one tank down to what is estimated to be an hour of fuel left, then burn the other tank until it's dry. Then they know more precisely how much fuel is left. It sort of does work like the motorcycle reserve.
jonnyjetprop
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Pilawt
Cessna Cardinals (even the early O-320-powered model) have a reservoir and engine-driven and electric aux fuel pumps (diagram below). The wings are set so low and so far aft that in extreme nose-up attitudes, fuel pressure to the engine can be insufficient with gravity alone.
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Velocity173
That's it. I've got a 5 gallon tank that sits behind the rear passenger seat that is pumped to the engine. That always has fuel that is fed from the left or right (30 gal a piece) tanks. Which ever tank is most full will override the other side and start to fill the sump. If you fly out of trim or if the aircraft isn't rigged properly then you can get an imbalance. Some canards have sight gauges for the mains while I have it on a digital display.
Dav8or
Final Approach
I guess I have flown planes with fuel sumps. I have logged hours in the Cardinal, the 172SP and the Grumman AA5.
Cogito
Pre-takeoff checklist
I fly the same plane, but by the time they built mine (8/13) the fuel selector option of "both" was removed (for reasons discussed prior.)
gismo
Touchdown! Greaser!
I generally do both engines simultaneously unless I'm sorting out a problem on one. Doing them individually wastes time, stresses the nosewheel structure, and can actually make it harder to catch an anomaly. I suspect that many if not most twin pilots that do their runnups individually do so simply because that's the way they were taught.
+1
I was never taught to do both at the same time, however, somewhere (I think in the King's Multi Engine vids) it was mentioned that running up both simultaneously puts less stress on the nose gear. So I started doing it that way.....
ARFlyer
En-Route
+1
I was never taught to do both at the same time, however, somewhere (I think in the King's Multi Engine vids) it was mentioned that running up both simultaneously puts less stress on the nose gear. So I started doing it that way.....
I've been taught since my first ME flight to do both at the same time. Both engines at 1500RPM and do the feather test. Then up to 2000 for the mag test. Both left mags are tested then the right. Quick and easy. It helps that the plane has digital RPM gauges.
gismo
Touchdown! Greaser!
One advantage of a simultaneous runnup is that most anomalies on one engine will be more obvious with the other performing correctly.
bluerooster
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shorty
We had one, but it didn't actually have a "both" selection, but it had 4 valves, and when all valves were positioned correctly, you were feeding from both tanks.
NoHeat
Final Approach
Maybe your bike is fuel injected.
I believe an on/off petcock is required on carbureted bikes because the tank is positioned above the carb, so that when parked the engine could flood with gas, if the fuel is not positively blocked by turning the petcock to the off position.Without the petcock in the off position, you would rely entirely on the carb float to not allow fuel to drain into the engine and flood it.
Not sure, but maybe in a high wing plane with gravity feeding fuel to the carb, the mixture knob serves a similar purpose for shutoff.
The bike lacks the mixture knob.
The petcock in many carbureted bikes had a reserve setting, which you could engage by reaching down just below your tank, even while riding. I'm not sure, but maybe this requires that the small reserve tank be located above the carb, which is easy to arrange on the bike, with the tank immediately above the petcock, which is immediately above the carb. Would the same configuration be awkward in a plane?
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brcase
En-Route
Maybe your bike is fuel injected.
I believe an on/off petcock is required on carbureted bikes because the tank is positioned above the carb, so that when parked the engine could flood with gas, if the fuel is not positively blocked by turning the petcock to the off position.
Not sure, but maybe in a high wing plane with gravity feeding fuel to the carb, the mixture knob serves a similar purpose for shutoff.
The bike lacks the mixture knob.
The petcock in many carbureted bikes had a reserve setting, which you could engage by reaching down just below your tank, even while riding. I'm not sure, but maybe this requires that the small reserve tank be located above the carb, which is easy to arrange on the bike, with the tank immediately above the petcock, which is immediately above the carb. Would the same configuration be awkward in a plane?
All the ones I have seen use just a small stand pipe as part of the valve so that it draws fuel a certian distance from the bottom of the tank in the normal position. In reserve it draws fuel from the bottom of the tank.
I suspect that Ron was correct in part. Even though it would be simple system, It is a bit more weight, complexity, and maintenance that manufactures struggle to keep to a minimum. However I suspect the main reason is that it would encourage pilots push fuel limits until they had to use the reserve. It would probably be an interesting study to see if this feature woud reduce or increase fuel starvation incidents.
Brian
NoHeat
Final Approach
Thanks Brian.
Here's an an illustrated explanation of the two-inlet one-tank configuration for a "reserve" on a motorcycle, and it is as you described.
http://faq.ninja250.org/wiki/How_does_the_reserve_tank_work?
Here's an an illustrated explanation of the two-inlet one-tank configuration for a "reserve" on a motorcycle, and it is as you described.
http://faq.ninja250.org/wiki/How_does_the_reserve_tank_work?
Jaybird180
Final Approach
Yes, I was poking fun at the carbureted motorcycle.
GCA319
Cleared for Takeoff
Is the hokey pokey really what it's all about?
Oh...wait...you meant aviation...
Oh...wait...you meant aviation...
GCA319
Cleared for Takeoff
Well here's one that I really should know (I'm a CFI after all), but don't. Why is it generally preferred to check the right mag before the left mag during the mag check? It's what I was taught and what I teach, but I've never really thought to figure out the "why" behind it..
Hank S
En-Route
Maybe because the first click of the key is "Right," so I check it first. Back to Both, then two clicks over to "Left." Note that these are the positions counted fron "Both" with the engine running.
Noah Werka
Pre-takeoff checklist
So was I, until early on in my career, some one who had a lot more experience than I did brought it up.
I do the "Left"(two clicks) first, back to "Both", then the "Right"(one click) and back to both. That insures that I will always be running on "Both" mags. Otherwise, only going back one click doing "Left", and it happens, leaves you running on only one mag.
Noah W
MAKG1
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MAKG
On at least some airplanes, the right mag is the left key position….
The reason I've heard said is that if you do the right mag (left key position) first, then the left mag, then both, you can't accidentally leave yourself on the left mag only for takeoff.
You can get the same result just by counting clicks and seeing that the RPM went back to normal before concluding the mag check.
The reason I've heard said is that if you do the right mag (left key position) first, then the left mag, then both, you can't accidentally leave yourself on the left mag only for takeoff.
You can get the same result just by counting clicks and seeing that the RPM went back to normal before concluding the mag check.
gismo
Touchdown! Greaser!
I don't believe that there's any valid reason to start with one or the other. Some pilots have a preference but their reasons likely only apply to them and are very unlikely to be universal.
There is a reason why some airplanes are started on a particular single mag.
weirdjim
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weirdjim
Actually, there is a reason. It is a lot easier to miss-index the switch key when you are checking the mags and run on only one mag when you think you have switched to "both".
Jim
gismo
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I've done it both ways and disagree. If the switch has no START position it's trivial to get back to both regardless of which single mag position you're coming from. And if there is a START position IMO it's just as easy to count two detents as it is to count one (assuming one is up to counting beyond one).
Furthermore if you feel it's likely you would fail to move the switch past two detents when finishing the check I'd say you were just as likely to make the same mistake when attempting to select the left mag for the check. Granted the consequences of a failure to check one mag are slightly less than taking off with one mag disabled but the better solution IMO is to visually verify that you've moved the switch(es) back to both at the completion of the check.
So like I mentioned in my last post, this is a preference. That said I'm all for having a "standard" way of performing the check that a given pilot sticks to.
EdFred
Taxi to Parking
If this is a problem for people, they probably shouldn't be flying at all.
MAKG1
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Agreed. Even if the ignition lock is a wildly worn POS, it should be obvious that the RPM drop is still dropped, prior to lowering the throttle and leaning the mixture.
gismo
Touchdown! Greaser!
I did manage to start a takeoff roll with the mag swith on Left once a long time ago while learning to tow gliders in a SuperCub. It wasn't the result of a faulty runnup though as no runnup was performed, the engine was started on the left mag and concentrating on launch procedures I plain forgot to check the mag switch. The CFI/pilot in the back seat noticed the mispositioned switch and rather than "fixing" it he announced it over the intercom which precipitated my next mistake (looking back at the switch located behind my back on the left side of the cabin). His next words "Fly the xxxx airplane" were spoken with a bit more urgency as I was drifting towards the corn having stopped pushing right rudder to turn and look back.
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Not good. EVERYONE who has owned a motorcycle with reserve has forgotten to put the valve back to the "on" position when filling the tank. That is one sinking feeling when the bike sputters, you reach down, and it's already on "reserve". It's going to be a long walk...
gismo
Touchdown! Greaser!
BTDT. At the time I concluded that it wouldn't be all that difficult to design a reserve valve that automatically reset, either when the engine was shut off or when the tank was filled. But that could fail too.
As to putting such a mechanism on airplanes, mine already has it. A fuel totalizer coupled with GPS gives a pilot the ability to generate a warning if the estimated fuel at the destination is predicted to be below some minimum.
With a mechanical reserve, there'd be a problem with the amount of the reserve. Sometimes a hour's worth is plenty, sometimes twice that isn't enough.
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jsstevens
That is how my primary instructor taught me and I've done it ever since. Makes sense to me.
John
dell30rb
Final Approach
Certified swift has two main wing tanks that are fed in a similar fashion. You fill from a single point too.
spiderweb
Final Approach
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Ben
I'm not worried at all. Not one bit.
spiderweb
Final Approach
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EdFred
Taxi to Parking
Finding something else to ***** about since you can no longer whine about your poor precious threads only getting a one star rating?