or Care and Feeding
of Pilot Lights
missed a bit of excitement that most of us would rather avoid.A
proper understandingof your pilotlightandburner systemcan
help youto avoid this type of excitement, or at least handle the
situationwithoutendangeringyourself and upsettingyour pas-
The modern hot air balloon burner, or inFAA-speak, “Air-
borne Heater” varies in some details between manufacturers.All
burners share following commonelements:
1.An output control.Currently an on-off valve, known as
blocks fuel flow to turn off the flame. The pilot controls the heat
outputby simplyturning the flame onandoff.
arrays ofsmall jets or nozzles or a venturi system to provide quiet
3.A vaporizingsystem.A systemof openorenclosed
coils is used to transfer heat from the flame to the liquid propane.
Thisheatchangesthe liquidpropane intovaporthatisforced
through the jets. The vapor mixes with the air, allowing it to burn.
4.An ignition source. Current systems use a standing pilot
failure, a flint andsteelweldingstriker or piezo-electric igniter
canprovide anignitionsource.A long-nosebutane lighteris
somewhat less reliable than a striker, so it should not be the only
A hot air balloon requires considerable heat for hot inflation
and sustained flight.Typical early burners produced outputs in
the range of 4millionBTU/hour, comparedwith more than15
million BTU/hour for modern burners.The actual output varies
with fuel pressure. At typical fuel pressures in the 100 to 125 psi
(pounds per square inch) range, output is proportional to the fuel
flow. Commercially available LP gas, typically amixture of92%
95,500 BTU/gallon.At 15 million BTU/hour input, the fuel flow
throughthe burneris157gallonsper hour, or2.6gallonsper
percent to 10 percent to support combustion. The ignition source
mixture.A pilot light provides a hot enough flame, and the pilot
light is located where it will encounter an ignitable mixture soon
after the blast valve isopened.
Pilot lights are supplied in two configurations – vapor feed,
and liquid feed.Two or more fuel lines connecting to one of the
fuel cylinders can identify a system with a vapor feed pilot light.
Asystem with a liquid feed pilot light will have only one fuel line
Both systems are normally quite reliable, but things cango
wrong.Several checks are performed duringanannualinspec-
tion.They include testing the pilot light vaporpressure, checking
the flame size, shape, and resistance to wind, and checking how
Failure of any of these tests can indicate a problem that must be
corrected before the next flight.
Avapor feed pilot light draws propane vapor from the vapor
space in the topof a propane cylinder using a separate fuel line.
pressure tothe pilotlight.Pilot lights operate like a laboratory
orifice or jet intoa tube withair inlets in its sides.It thenmixes
withair, and maintainsa flame atthe topof the tube.
With avapor feed pilot system, the pressureregulator and the
adjustable regulator may be adjusted, but a fixed regulator must
be replaced if it fails.A partially clogged orifice can sometimes
be cleaned using a mild acid solution and compressed air.If that
burners, itcan be drilledwitha fine machinist’sdrill).
Aliquid feed pilot system is more complex than a vaporfeed
system.It uses either a vaporizing chamber feeding an adjustable
parts.With clean fuel, neither system should cause any prob-
lems.Sometimes impurities in the propane do not vaporize.
These impuritieswillleave a tar-like residue inthe vapor genera-
tor, sometimes cloggingit or preventing itfrom operating prop-
erly.Disassembly, cleaning, and some partreplacement may be
A pilot light failure mayoccurwithout warning.More
frequently, you will find that it occasionally blowsout in a wind
shear, or makes more or lessnoise than usual. Some burnersvent
any fuelthat leakspastthe blast valve stem sealthrough the pilot
light, so an unusually tall pilot flame may indicate a blast valve
problem. Your repair stationshouldcheckanyunusual pilotlight
If the pilot light flames out inflight, your immediate task is
tolightthemainburner.Don’t attempttotroubleshoot the
pilot light system untilthe mainburneris lit and youhave
achieved level flight or a climb to a safe altitude.The second
task is tofind a safe landing spotandland as soon as practical.
Practice lighting themain burneron the ground until you can
alwayslightit within2 strikes.
The following hints should improve your success rate:
2.Look at the burner anddetermine the pilotflame loca-
tion.Theburner designer putthepilotflame whereitshould
3.Practice placing the striker veryclose to thatlocation,
5.While holdingthestriker intheproper location, mo-
mentarily open and close the blast valve, to release a small cloud
of fuel.You need a mixture between2 and10 percent propane
– too muchfuel will not ignite.
6.Strike a spark.You should hear the flame when you do
that.If youdo not, strike 2 or 3more sparks.
7.Repeatsteps 5and6 until youget a flame.
8.Quickly open the blast valve for your burn.
9.If the pilot light doesnot relightwiththe mainburner,
you can partially open a vernier valve, a cruise control valve, or
maintain a flame that will ignite the main burner.
expect everyone toget 100% correct.