**4.5 Lighter-Than-Air Operations:**

Special nature of lighter-than-air flying

Types of lighter-than-air vehicles (hot-air balloons, cold-air balloons,
blimps)

Hypoxia

Trapped gas expansion

Thermal stress

Crash survival and crash worthiness

The first human flight occurred on November 21, 1783, when two Frenchman
ascended in a hot air balloon built by the Montgolfier brothers. A month
later, a gas balloon filled with hydrogen, designed by Jacques Charles,
also flew in France. Since that time, ballooning has had a unique role
in aviation and is the oldest form of flight. Primarily, free ballooning
is a sport activity in the United States, although powered ballooning,
technically referred to as an airship, has limited commercial
operations, primarily for advertising and television photography of
sporting events. The return of airships to cargo operations and
passenger carriage continues to be an elusive mirage. Balloons retain
the right of way in all aviation operations, over helicopters, gliders
and powered aircraft.

![](media/image1.png){width="5.30625in" height="4.729861111111111in"}

The Montgolfier balloon, c. 1783

There are three kinds of lighter-than-air vehicles. These are the hot
air balloon, which is simply an empty bag, fueled by an open flame below
it, usually propane-fired. Cold air or gas balloons have recently been
reintroduced into sport ballooning, only since 1995, with the commercial
availability of helium in fairly economic amounts. These two sorts of
balloons are very limited, because of the lack of directional control.
Effectively, the balloon pilot, who is not required to have a medical
certificate unless operating commercially, can only control the altitude
of the vehicle. This is done either by controlling lift from the gas
bag, either by heating the hot air more, in the case of a hot air
balloon. However, lift is limited in a gas balloon. Special balloons
made of ultra thin mylar were engineered to permit flights into the
stratosphere during Operation Man High in the 1950s. The pilots, Capt.
Joseph Kittinger and Dr. David Simon, parachuted back to earth, with
Kittenger's leap from a record setting altitude of 102,800 feet in
August, 1960.

![](media/image2.png){width="2.6041666666666665in"
height="1.9479166666666667in"}

Kittenger's leap, photographed from the Man High III gondola camera.

![](media/image3.png){width="2.375in" height="1.9791666666666667in"}

Fossett's 'Spirit of Freedom' in flight

A new development is the compound gas/hot air balloon. Inside the outer
envelope, there are two lift bags, one of helium and the other of hot
air. A compound balloon was used by Steve Fossett to circumnavigate the
globe in 2002.

The altitude can also be adjusted by altering the weight of the vehicle
can also be altered by releasing ballast. Today, this is usually in the
form of water or sand. Directional control in balloons is at the will of
the winds, but the wind direction and intensity varies at different
altitudes. Often only a few hundred feet of altitude change will find a
new wind direction and intensity. The balloon pilot will attempt to
alter the direction by changing their altitude and thereby selecting the
available wind to carry the balloon as desired. This obviously makes it
very difficult to preplan a flight course, and most ballooning takes
place at a relatively low altitude of less than 5,000 feet above ground
level.

![](media/image4.png){width="3.1381944444444443in"
height="2.217361111111111in"}

**CargoLifter CL75 AirCrane, Capital Increase-one of the few operational
commercial cargo airships.**

More complicated is the airship. All airships today are blimps, a
non-rigid gas balloon that is slightly more complicated than its
unpowered brethren. The blimp consists of an internal gas bag called a
balloonet, which contains the actual lifting gas. Enveloping the
balloonet is the outer envelope which provides aerodynamic structure,
but permits the balloonet to vary in size. This is because the pilot
will wish to alter the amount of lift available in flight, and heating
during a prolonged flight may cause the gas to expand or contract.
Careful preflight planning is required.

![](media/image5.png){width="3.6395833333333334in"
height="2.859722222222222in"}

Photo blimp operations

Because airships are powered by engines, usually internal
combustion/propellers, the pilot must carefully plan weight in advance
and anticipate that the net buoyancy of the airship will be zero at the
completion of the flight. This means that on takeoff, at a minimum, the
airship will be heavy by the amount of fuel anticipated to be burned,
and the airship pilot uses the dynamic lift of the horizontal tail plus
thrust of the engines. An airship also has vertical rudders and tail
fins, and thus the controls of an airship are different from an
aircraft. There will be foot controls for the vertical rudder and a side
wheel for controlling the horizontal rudder. However, there is no
"stick" as in an aircraft, because an airship has no wings. Throttle
controls may be variable, and many modern airships have steerable
engines on pods.

Because balloons and airships operate at relatively low altitudes,
hypoxia is rarely an issue, and trapped gas is rarely a problem,
although it always is a critical issue for the lifting gas of the ship
itself. Thermal stress may be fairly high in some operations. Many
balloon operations take place in deserts, where the climate and terrain
is benign. The world\'s largest balloon event takes place at
Albuquerque, New Mexico every year, where over 1,000 hot air balloons
and gas balloons participate. Medical certificates are not required of
balloon pilots, if they are holding a student, private, or instructor
certificate.

The majority of balloon operations world wide are recreational hot air
balloons. Thousands of people take hot air balloon rides as one time
tourists. The typical flight is very early morning takeoffs, when the
air is still. A basket beneath the balloon may carry a dozen passengers
and a commercial pilot.

![](media/image6.png){width="2.502083333333333in"
height="3.779861111111111in"}

Shasta Valley Balloon at sunrise, Mt. Shasta. ©Jane English, with
permission.

The major health issue with lighter than air operations is landing. In
particular, hot air balloons and gas balloons have crew compartments
that are basically a modified basket, since all landings are "out", that
is, they are away from a prepared landing site. There are many risks
involved in landing, most notably, striking power lines and trees, or
being caught in sudden adverse weather with high winds. The fragility of
the baskets, in order to conserve weight, leads to most of the traumatic
injuries and deaths involved with lighter than air operations, although
these are uncommon.

Reference: Ballooning Federation of America