Avionics Engineering

What’s That White Smoke/Mist On Aircraft That Blows Into The Cabin?

Once followed the aircraft as a flying spanner and that time we reached Huahin Thailand. There was one passenger who noticed white mist/fog coming down from the vents above from cabin sidewall louvers and ceiling and he freaked out and refused boarding until I had to explain to convince him and assure him things are safe.

The white mist you often see in aircraft cabin during air conditioning packs operative is nothing more then condensation caused by moisture in the air (humidity) being cooled to the point where the humidity becomes visible. This is a good example of what fog or clouds, which is called the dew point. It is the air temperature to which air must be cooled at constant pressure and water content to reach saturation. The higher the dew point temperature the more uncomfortable it becomes due to the high humidity. In highly humid area or weather conditions, the air does not need to be cooled very much to exhibit this phenomena, and once the dehydration of the air is accomplished, the visible condensation disappears.

Even simple example on a hot day just go and open your Freezer and you will see similar fog/mist coming out.

LIGHTING, AIRCRAFT, NIGHT VISION IMAGING SYSTEM (NVIS)

MIL-STD-3009 (SUPERSEDING -> MIL-L-85762A)

This standard establishes requirements for the emission characteristics of aircraft
lighting and display equipment that is intended for use with night vision imaging systems
(NVIS). It is applicable to all systems, subsystems, component equipment, and
hardware that provide the lighting environment on aircraft where NVIS are employed.

Night Vision Imaging System (NVIS).
A system that uses image intensifier tubes to produce an enhanced image of a scene in
light conditions too low for normal navigation and pilotage.

By design, the MIL-L-85762, ASC/ENFC 96-01 and MIL-STD-3009 were kept general
so that they could be used by a wide variety of users. Also, in some cases,
compromises had to be reached among the services so that a tri-service specification
could be achieved. However, where compromise was needed, it was almost always
conservative. Therefore, some project managers may want to waive parts of the
standard. However, caution should be used because, although not readily apparent,
many parts of the standard are interrelated. For example, specifying NVIS Green as a
color is no guarantee that NVIS-compatibility will be achieved. Likewise, changing the
color could make achieving the proper NVIS Radiance impossible.
Throughout the development of MIL-L-85762 and MIL-L-85762A, the JACG members
received numerous complaints from manufacturers that the requirements were
unrealistic, impossible to meet, or excluded certain technologies. However, it has been
proven that these manufacturers are incorrect and, at the time of this writing, numerous
manufacturers can meet the requirements of MIL-L-85762. Likewise, red lighting
components meeting the requirements of MIL-L-85762A are difficult to manufacture at
the present time. However, after manufacturers have had an opportunity to examine
the requirements and develop product lines to meet those requirements, the red lighting
components should also be readily available.

Tool Chain for Avionics Design, Development,
Integration and Test

Must Read.

ceur-ws.org

Clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet.

The atmospheric region most susceptible to CAT is the high troposphere at altitudes of around 7,000–12,000 metres (23,000–39,000 ft) as it meets the tropopause. Here CAT is most frequently encountered in the regions of jet streams. At lower altitudes it may also occur near mountain ranges. Thin cirrus clouds can also indicate high probability of CAT.
CAT can be hazardous to the comfort, but rarely the safety, of air travelers.
CAT in the jet stream is expected to become stronger and more frequent because of climate change, with transatlantic wintertime CAT increasing by 59% (light), 94% (moderate), and 149% (severe) by the time of CO2 doubling.

Jet stream:
A jet stream alone will rarely be the cause of CAT, although there is horizontal wind shear at its edges and within it, caused by the different relative air speeds of the stream and the surrounding air. Rossby waves caused by this jet stream shear and the Coriolis force cause it to meander.

Temperature gradient:
A temperature gradient is the change of temperature over a distance in some given direction. Where the temperature of a gas changes, so does its density and where the density changes CAT can appear.

Gravity wave wind shear:
Beneath tropopause, the air gets colder and the wind gets faster with height. Above it, the air warms and wind velocity decreases with height. These changes in temperature and velocity can produce fluctuation in the altitude of the tropopause, called gravity waves.

The Quaid e Azam Muhammad Ali Jinnah Aircraft - Viking 1B

Vikers Viking 1B-J750 aircraft was manufactured by Vikers Armstrony of UK. It was designed to fulfill the commercial needs of passengers and freight transportation.

Pakistan Air Force operated this, specially built VIP version, known as Viking 1B-J750. This aircraft had additional navigation aids as well as VIP configuration seating and internal layout. It was first flown in August 1946 and used by PAF in 1948. It had two piston engines, Hercules 634, fourteen cylinder radial air-cooled engine; with a thrust of 2 x 1690HP. Its maximum speed was 263 mph and climb to a height of 23,200 feet.

This aircraft was in the personal use of Quaid-e-Azam Mohammad Ali Jinnah, the founder and first governor-general of Pakistan, till his death on the 11 September 1948; when he flew from Quetta to Mauripur (now Masroor Air Base).

Group Captain Mian Atta Rabbani was the first ADC (Aide-de-Camp) of Quaid-e-Azam. He was also the first pilot to be transferred from the Royal Indian Air Force to the Royal Pakistan Air Force in the newly-born state of Pakistan. Later, this aircraft was retired in 1953 and preserved in one of the world-renowned aviation museums in Karachi known as Pakistan Air Force Museum.

More Details History Page:
http://www.historyofpia.com/board/november_07/viking_nov18.jpg