Heat Exchanger Cleaning

Summer already started and ambient temperature is now getting higher and higher everyday until September when it will start to drop again.

In hot weather like this, the airconditioning system (a/c) will have to work harder in order to produce sufficient cool air to chill out the cabin. The heat exchanger is part of airconditioning system where transfer of heat from the engine bleed air back to ambient before the air further process by the air cycle machine (heart of a/c system) to produce cool air.

With dusty enviroment such as here in middle east, the dust or dirt can accumulate in between the fins of the heat exchanger thus reduce the efficiency. Cleaning of the heat exchanger is necessary, with heat exchanger backfush cleaning process.

Here is the photo that i took while we doing it on one of the BBJ, the mix of hot air and water was injected from backside of the heat exchanger so it force out the dust and dirt that trapped inside the heat exchanger itself.

There is slight improvement for the output of the a/c system after we did this, however with ambient temperature of 45 deg C, getting sufficient cool air out of the a/c is seems difficult, we still need the use external ground airconditioning cart.  

How To Change Aircraft Wheel

Ever wonder how the replacement of aircraft wheel been done? With big in size and heavy in weight, without special tools it will be imposible to be done. Here is the general description of it so that all of us have some ideas how it is done.

Depend on the organisation, in the company that currently i work with, we had a wheel change trolley where the new wheel is placed as well as the nitrogen bottle needed to charge the wheel.

Aircrat will be jacked from the axle to raised it up from the ground, then one and only nut that hold the entire wheel will be loosen and unserviceable wheel ready to be removed by sliding it out from the axle.

With the wheel dolly, which can be raised and lowered, the weight of the wheel will be supported and the wheel will be slide out from the axle, later on the new wheel be placed on the dolly and slide back to the axle.

The big nut again will be tightened and torqued to certain level to ensure proper sitting of the bearing sof the wheel, then it will loosen again and final tightening at lower torque to secure the wheel.

Take note that on B737 BBJ, the only thing that hold the wheel is this big nut on the left, however this big nut is secured by two extra bolt to prevent it getting loose during operation.

Pre Refueling - Water Check

Prior to carry out refueling of an aircraft, the quality of the fuel from the fuel truck (bowser) must be checked to ensure it cleanliness as well as the present of water. Dirty fuel can caused fuel filter clogged and water can frezzed at high altitude during flight thus blocking the fuel going to the engine.

Normally at the bowser, there a small glass container in which fuel sample from the bowser can be collected. Visually we can check the cleanliness. To check for presence of water, we need to use the water detector capsule.

With water detection capsule attached at the front of the shringe, the fuel that been suck will pass through it. The capsule contain chemical that will change colour when exposed to water molecule.

If no water molecule present in the fuel, the capsule colour will remain unchanged from the original which light yellow.

This is what happen when the water introduced to the capsule. Turned dark blue which indicate the present of water.

So far i never had an experience this test failed from most of the fuel supplier around the world, aircraft fuel is high quality kerosene that been processed through very strict high quality standard to ensure safety operation of an aircraft.

Thanks to Benny from Cotonou, Benin which coorperate & enable me to take the photo of the test.