cessna 310 questions
gross_arrow
1. we had the micro-aerodynamics vortex generators installed. they claim
a 10 mph reduction in vmc and a 5 mph reduction in stall. now i know
they work by 'disturbing the boundary layer'. what i don't know is what
effect this has on the stall _warning_ vane. would the stall warning be
'calibrated' to the old (faster) stall speed, or would it just naturally track
the reduction in stall speed? (i don't know enough about aerodynamics
to know).
2. the preflight checklist calls for checking the "sniffle valve" opening to be
free of obstructions. nowhere in the manual is the "sniffle valve" defined
or described. i have asked 2 mei's and 2 mechanics, and none of them
has known what the "sniffle valve" is. help?
thanks,
gross_arrow
(may need to change the handle to "gross_310")
Mike Rapoport
would be unaffected by VGs.
A sniffle valve is installed on fuel tanks to allow for the expansion and
contraction of air inside the tank. The ones on a MU-2 are red with a hex
head and you can see a spring and the piston in the middle. I would
recommend against opening the valve as a check since this always seems to
cause the valve to leak ever after. I am surprised that you have them on a
piston plane. They are required in the MU-2 because the tanks are
pressurized by bleed air to transfer fuel so you can't have a conventional
vent system. I thought all the tanks on a 310 transferred with electrical
pumps?
Mike
MU-2
"gross_arrow" <gross...@yahoo.com> wrote in message
news:cb365b61.02052...@posting.google.com...
Ronn Walker
aft of the fuel cap. It has a small fairing covering it. The opening faces
aft and you can look inside of it.
JerryK
as the Seminole have them also. The tip tank Cessnas have both electric and
mechanical pumps. On my 340 the mechanicals are the primaries and the
electrical are used for priming and vapor supression. In addition there are
pumps in the tip tanks that transfer fuel from to the pickup pump to prevent
unporting durring decents.
jerry
"Mike Rapoport" <rapo...@ix.netcom.com> wrote in message
news:uesvp34...@corp.supernews.com...
Mike Rapoport
realized that sniffle valves would be necessary.
Mike
MU-2
"JerryK" <jer...@nospam.com> wrote in message
news:lITH8.104127$UV4.200047@rwcrnsc54...
gross_arrow
> The sniffle valve is located on top of the main (tip) tank on the 310, just
> aft of the fuel cap. It has a small fairing covering it. The opening faces
> aft and you can look inside of it.
thanks. i shouldda read the news before i went flying yesterday,
so i could check this out. now it'll be thursday before i get back to the
airport to look at these. once again you have proved that this is
more than just a pretty newsgroup: you learn "stuff" here.
thanks also to mike and jerry for their replies.
gross_arrow
gross_arrow
> as the Seminole have them also. The tip tank Cessnas have both electric and
> mechanical pumps. On my 340 the mechanicals are the primaries and the
> electrical are used for priming and vapor supression. In addition there are
> pumps in the tip tanks that transfer fuel from to the pickup pump to prevent
> unporting durring decents.
>
> jerry
>
thanks jerry -- the 310 is pretty much the same. the manual says that the
electric pumps provide 9 psi of pressure at low. switched on high, they
also provide 9 psi, unless the mechanical pump fails, in which case they
provide 20 psi. so i'm presuming they have some way of sensing the
failure of the mech. pump.
the 310 also has the 'submerged' tip-tank pumps that 'tick' loudly when
the master is on. they are on the landing light circuit breakers. i have
read the manual through several times, and when i went to pick up the
310 from getting the pitot-static/xpndr check done, i 'passed' my first
'exam' -- the maintenance guys had pulled the landing light circuit
breakers while checking out the xpndr and neglected to put them back
in. i turned on the master, heard no clicking, and immediately went to
the landing light cb's.
(some of us get really excited over small successes.)
gross_arrow
Cary Mariash
belonging to the same class as the newer planes. However, I still think
of my 1958 C310B as a 310 with a tip tank. However, this plane does not
have sniffle valves. The electric pump is used only for priming and for
take-off and descent in case the engine driven pump fails at these
critical times. It is not required when changing takes to the aux or
cross-feeding. I don't know when the sniffle valves were installed, but
I bet they came latter than 1958 or 1959 (the C model is similar to the
B model except for converting the carb to fuel injection).
Cary
In article <lITH8.104127$UV4.200047@rwcrnsc54>,
"JerryK" <jer...@nospam.com> wrote:
> 310s and all tip tank Cessnas have sniffle valves. Other piston twins such
> as the Seminole have them also. The tip tank Cessnas have both electric and
> mechanical pumps. On my 340 the mechanicals are the primaries and the
> electrical are used for priming and vapor supression. In addition there are
> pumps in the tip tanks that transfer fuel from to the pickup pump to prevent
> unporting durring decents.
>
> jerry
>
>
--
Cary N. Mariash
CP-ASMEL/IA
N500QB (1958 C310)
JerryK
Sorry for the overgeneralization.
"Cary Mariash" <ca...@lenti.med.umn.edu> wrote in message
news:cary-6B86E3.1...@news.newsguy.com...
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JerryK
of two possible ways the fuel system works. A lot of 3xx Cessnas have
MEB88-??? (I forget the number). This replaces the automatic system you
describe with one that is manual. One way to tell is look at the fuel pump
switches. If have a detent you have to lift over before the switch goes
into "high" then you probably have the MEB88 kit installed. If you have
this system, you must manually put the pump in the high position if you lose
the mechanical fuel pump.
BTW, the tank pumps you are hearing are a no-go item. Don't fly the plane
if one is not operating.
jerry
"gross_arrow" <gross...@yahoo.com> wrote in message
news:cb365b61.02052...@posting.google.com...
gross_arrow
well, i went out last night and flew again. and there was no fairing
or valve on top of the tip tank.
drawing on the information in replies from mike rapoport and jerry, i'm
getting the picture that perhaps sniffle valves are present when there
is a mechanism to transfer fuel into the tank (from another tank). the
'65 310 i own had available at time of ordering one or two wing locker
tanks. if these wing locker tanks were installed, they could not feed
the engines directly, but their fuel was to be pumped into the main
(tip) tanks. my plane does not have the optional wing locker tanks
installed. therefore, perhaps i do not have the sniffle valves.
this is not inconsistent with other parts of the preflight checklist. for
example, it calls out checking the oxygen quantity and the oxygen
on/off knob, and my plane was delivered without oxygen (at least
as far as i can tell from the logs, an o2 system was never 'de-installed'
and it doesn't have one now.) so, it seems apparent that the check
list covers available options rather than installed ones.
i also flew with another mei last night, and he had no clue about the
sniffle valves. he had ~25-30 hours in 310's.
so, i'm still researching, but i'm beginning to think that that particular
checklist item does not apply to my airplane.
thanks for all the replies, and if anyone else has any insight, please
pipe up.
gross_arrow
Bill Hale
>
> 1. we had the micro-aerodynamics vortex generators installed. they claim
> a 10 mph reduction in vmc and a 5 mph reduction in stall. now i know
> they work by 'disturbing the boundary layer'. what i don't know is what
> effect this has on the stall _warning_ vane. would the stall warning be
> 'calibrated' to the old (faster) stall speed, or would it just naturally
The stall warning on these senses angle of attack.
The angle of attack at stall will be higher with the VGs than without.
Otherwise the stall speed would not be reduced--which it is.
So the stall warning will come on at the same angle it did before
you added the VGs. It will come on too soon.
They tend to ignore this small feature.
Also note that your maneuvering speed is correspondingly reduced.
And since the stall is reduced, practically speaking 1.3 Vs can
also be reduced. If you don't, you will float a long way down
the runway. The supplements, if any, are usually pretty
quiet on these points.
Bill Hale BPPP Instructor
Chad Lemmen
a sniffle valve under there I just thought it was a vent. If my tanks get
filled too full sometimes during climb fuel will exspell out of that valve. Is
this the purpose for having the sniffle valve? I don't have the wing locker
tanks installed either, but I still have those valves.
Mike Rapoport
pressure. Over pressure arises when you climb or the tank heats up on the
ground and the fuel expands. Under pressure arises when you descend or when
air in the tank cools. In my airplane the sniffle valves operate at
+5.5psid and -.5psid. You are lucky that yours are located on the top of
the tank as sniffle valves like to leak.
The valve shouldn't expel fuel during climb. I'd suspect that your valves
are leaking.
Mike
MU-2
"Chad Lemmen" <ch...@lemmen.com> wrote in message
news:K8PJ8.226$2n4...@nwrddc04.gnilink.net...
JerryK
> are leaking.
>
Fuel streaming back is very common. In fact in some POHs there is a message
telling you that fuel will leak out of these valves. It is another reason
you don't want to overfill the tanks.
jerry
Mike Rapoport
> > The valve shouldn't expel fuel during climb. I'd suspect that your valves
> > are leaking.
> >
>
> Fuel streaming back is very common. In fact in some POHs there is a message
> telling you that fuel will leak out of these valves. It is another reason
> you don't want to overfill the tanks.
>
> jerry
>
>
fuel when their set preasure is exceeded. This usually happens on the
ramp with full tanks on a warm day. In flight, temperatures are
generally lower than on the ramp so if it isn't leaking on the ramp it
shouldn't leak in the air. If it is expelling fuel in flight then the
valve probably isn't sealing properly. They often get debris between
the sealing surfaces and susequently start leaking. They are a PITA
IMO.
Mike
MU-2