Hydraulic Leak in Aircraft System

Aircraft hydraulic is a very complicated system with a lengthy plumbings, joints, connections, valves, pumps and so on. As the aircraft aging, especially on component where the seals start to deteriorate, leaks can occur. This is most common findings during routine inspection on aircraft especially in the wheel well area.

Any leakage found should be treated promptly however it is not economical to keep changing any component that have started to leaks. There is an allowable limit set by the manufacturer which allows aircraft that have leakage on its component to be release for flight after details of the leakage been recorded.

In the maintenance manual, the allowable limit basically is how many drop per minute. It further will be specified static or dynamic which is with component is off condition or operational. Aircraft engineers will switched on the relevant aircraft hydraulic system and observed the leaks to find whether it is within limit or not. If out of limit then the component must be changed before next flight.
Not all leakage is allowable, on plumbing connection for example leakage is not allowed at all. With 3000 psi pressure (that is normal operating pressure for most aircraft) any leakage can drain whole system fluid, the good news is that normally there is 2 or 3 independant hydraulic system available on an aircraft so if one system is down, there is still a backup.

All pics sample of leakage is from the aircraft wheel well.

Aircraft Maintenance Engineer - Unknown facts by non aviator

When we are in the airport, a lot of times we can see the pilots and cabin crew walking by us and begin admiring their glamorous career on board the aircraft, but do we know who is the one responsible for the maintenance aspect of the aircraft that they working on? That person is Licensed Aircraft Maintenance Engineers, he is the one responsible to make sure that an aircraft is save to fly, to carry passengers or cargo's from one point to another point.

All aircraft maintenance engineer must have a license from local aviation authority to exercise his privilege which is to certify that an aircraft the he had inspected is fit for release to service.

How to become an engineer? Well, first of all you must have an interest on the aircraft itself because if you don’t like it or feel that there is nothing special about an aircraft then it will be more likely that you will not pass the exam or test to get the license. Practical knowledge is essential as it will make it easier to answer the questions in the license exam.

There is a lot of aircraft maintenance engineer training school that offering course to become an aircraft maintenance engineer, in fact Malaysia Airlines as well as Air Asia does have their own training department to recruit new aircraft maintenance engineers.

Training normally will took around 4 to 5 years, Malaysia Airlines for instance will provide an allowances to the trainees that join their training program however they will be bonded for few years once the trainee succeed his training program and established as licensed aircraft maintenance engineer.

Aircraft maintenance engineer can be divided into few categories, it can be Line Aircraft Maintenance Engineer or Base Aircraft Maintenance Engineer, apart from that they furthermore can be divided into trades that they are rated which is either Airframe Maintenance Engineers, Engines Maintenance Engineer, Avionics, Electrical or Radio. Aircraft Maintenance Engineer can be multiple trade as well. Normally Airframe Engineer will hold Engine license. Electrical, Avionic and Radio Aircraft maintenance engineer normally has all 3 rating with them.

Line Aircraft Maintenance Engineer normally attached in front line of service as they handle the aircraft for departure or in transit in the airport terminal while Base Aircraft Maintenance Engineer is the person who will inspect an aircraft when it is in the hangar for major inspection.

For trade classification, Airframe Maintenance Engineer will responsible to the defect or inspection related to the airframe part of an aircraft which is the fuselage, flight control, hydraulic, air conditioning system, including the passenger seats and so on. Engine Maintenance Engineer for the engine and auxiliary power unit of an aircraft, same goes for other trade. However only Airframe and Engine rated aircraft maintenance engineer has the privilege to release an aircraft back to service (flight) as a whole, for instance if there is a defect of electrical component, electrical maintenance engineer will rectify it however he will only certifying whatever job he did, before the aircraft can fly, the airframe and engine engineer then inspect the aircraft base on the inspection procedure laid down by the manufacturer and then certify that the aircraft is safe to fly. Certification will be in a form of signature plus the approval number from authority or company, stamped or be wrote down on the aircraft legal document which will be on board. One copy of the signed document will be leave on the ground before the door of the aircraft close for departure.

Once he put his signature in that document, he is responsible for the safety of the aircraft, the passengers, the cargo as well as the crews. Anything happen to the aircraft, licensed maintenance engineer that released the aircraft for flight will be the one that will be called by the aviation authority for an investigation. Base on this information I’m sure know the readers will realize who has the biggest responsibility once the aircraft lift off from the ground.

Dr Marten - Aircraft Maintenance Engineers official shoes

I just bought myself a pair of low cut black Dr Marten shoes for myself when i was in London. It cost me 50 pounds. Dr Marten shoes become common to aircraft maintenance engineers (AME) due to it oil, fat, acid and alkali resistance. Beside that it bouncing sole is really make it very comfortable to wear.

This is my third Dr Mart actually however to my surprised, it is no more made in England, instead it is now made in Thailand, huh.. globalisation... anyway seems the finishing and quality almost the same, the only different now for sure Dr Mart company profit will soar.

Dessert For VIPs

Most of the food served onboard the aircraft is way above standard of commercial airlines, of course if compare with economy class. Even on some airline that i flew on first class, the food served not as marvelous as what been served onboard our BBJ.

This chocolate cake by Paind'or was uploaded onboard in Lebanon, surprised me that in Lebanon this luxury cake is available there.

Below is cheese cake from Riyadh itself, is it yummy?

Tips From VIP

One of the interesting part of flying with the VIP’s is, most of them very generous especially the princes and the princess. The more difficult the flight which is like long waiting time, long flight such as to United States which very tiring to the crew, most of the time will be well compensated.

I take this shot to give you some idea what I’m talking about. Before landing or sometimes after VIP disembark, cheif pilot will distribute the envelopes of tip money. It’s depend on luck as well, sometimes there is a VIP that always give good amount of tips however when he or she in a bad mood, all of the crew will be left without any envelope.

Wanna know maximum amount I received? Put your guess in the comment, I will let you know after 10 guessing.

ps: Photo taken after i finished my shopping in Boston.

Refueling the aircraft.

How many of us really knows how refueling of an aircraft is done and where is the fuel tank for an aircraft is located? Probably not many know as well what type of fuel aircraft used. Aircraft fuel which is basically a highest grade kerosene will be pumped up by the fuel truck using the hose connected to the refueling panel.



At the fueling panel which is normally on right hand side of the aircraft wing's on majority of the aircraft, there is a control switches that open and close shut-off valve for each tank that fuel have to be added to achived total amount of fuel required for flight.

Aircraft fuel tank in general devided in to 3 main area, inside both wings itself as well as under the fuselage which is inside the body of the aircraft itself. Fuel tank in the wings will be filled up first before the fuselage. If happen that you sit in the middle of the aircraft next to the wing area, take not that below your feet is where the fuel tank is located.

Oxygen Bottle & Main Batteries

I have to change the crew oxygen bottle the other day and i want to share something that is unique about B737 NG which is the crew oxygen bottle and two main batteries are next to each other. On BBJ's that i work on 3 out of 4 don't have external panel for crew oxygen servicing so basically we have to change the bottle every time it drop below dispatch limit.

Located in E&E bay (avionic compartment) however to change either the batteries or the oxygen bottle, access from the forward cargo is required. Forward bulkhead of the forward cargo need to be removed for access. The panel secured with quick release fasteners which make it easier to be removed.

What I'm trying to highlight here is, in my opinion as well as other working mate that I've spoken with, we are surprised to saw this condition as batteries and oxygen which both is considered very sensitive and dangerous item positioned next to each other. I guess Boeing have calculated all the risk to allow this configuration.

Birdstrike on radome.

Aircraft arrived back with sign of birdstrike on nose radome, inspected and tap test test to determine any delamination found nil damaged apart from paint flaking.

Further inspection carried out on landing gears, airconditioning intakes and engines show no secondary damaged. Checked with pilot for any changes in engines parameters found nil problem.

The impact area cleaned-up and aircraft is ready to fly back. Of course now we are waiting for replacement radome as it looks very unpleasant especially for a VIP aircraft.

Hydraulic System Transfer

Hydraulic system on B 737 divided into 3 system which is A, B & Standby however only A & B system quantity shown in the system page on lower display unit. Standby system reservoir is connected to system B.

It can happen that few amount of hydraulic fluid did transfered to one another during flight even though theoretically it's not posible. It can happen through movement of shuttle valve that connect both system together when it supplied as back-up such as alternate brake. To normalise it back basically we need to drain it and replenish another system system with new fluid.

Experienced 737 engineer know the trick to transfer it with-out to drain and topping-up. Here i would like to share you the trick. From the photo we can see system B is higher, now to transfer from B to A.

1. Turn on B emdp pump.
2. Set park brake.
3. Turn on A emdp pump.
4. Turn off system B pressure by operate the flight control
5. Release park brake.
6. Turn off system A emdp pump.

After few repetition we can see the fluid transfered to another.

* This is just for information sharing and not to replace the aircraft maintenance manual procedure.

View of Nile

I was on the way back from Alger, Algeria to Riyadh when our aircraft pass through Egypt, what a view as i can see how Nile River green-up Egypt. On both side of the river there is only desert but what the river contribute to the land is very amazing.

Accident in Luton Airport

Mar 20th 2007 Luton Airport.

Mid size jet was parked infront of my aircraft after it has been placed at overnight parking bay. I was in impression that aircraft will be towed to taxiway and taxi out for takeoff however it is not, due to the jet blast from the engine start, the passanger step placed next to my aircraft was blown away and hit number 1 engines inlet lip.

Damaged assesment found it is out of Structural Repair Manual limit for normal flight, measurement taken and forwarded to Boeing for evaluation. Boeing granted approval for 1 ferry flight and 1 revenue flight.

Depart next day to Agadir as ferry, night stop for 8 hrs and head back to Riyadh next day as revenue flight.

Lucky it was only a dent, if it a puncture, for sure i have to stay in Luton at least for 1 week. Nice place to stay but with very temperature almost 0 deg Celcius, back home is much better.

Hydraulic Pressure Module Leakage

I was in Kuwait for 2 days trip, after landed and parked infront of VIP terminal in Kuwait Airport, i've noticed hydraulic fluid accumulated below system B hydraulic pressure module, from my observation i suspect it is from System B Hydraulic Electrical Pump pressure transmitter however it cannot be confirmed even with pump turned on , I've cleaned the area and wipe it dry, ready to be verified on next flight.

The next day after flight back to base, confirmed the leakage was from the transmitter base, as per IPC (Illustrated part catalog) there is a seal inbetween. Ordered and replaced the seal, ground check no leak as well on subsequent flight... problem solved...

Landing Gear Shock Strut Leakage.

During all this years i'm working on B737 NG, leakage on the main and nose landing gear strut is common on all aircrafts that i've worked with either Mastar or on current fleet.






I'm sure if someone unfamiliar with this situation will thinked that the this landing gear is having a problem of leakage however it is not.






As per Boeing Maintenance Tip document, this is because of new design on new 737 landing gear, thin layer of oil presence everytime the shock strut extended and this layer plus dirts that have sticked to it has been push down by a scraper seal as the shock strut compressed.


A follow-up maintenance action have to be carry-out after few hundred hours of aircraft operation, this is to ensure sufficient amount of fluid remain in the shock strut itself.

Nose Gear Low Extension

I was in Seoul, Korea from 9 Feb to 15 Feb 07, upon arrival in Incheon Airport during my walkaround check found nose gear strut with very low extension. Only 1 inch of the chrome part visible. Since tired of long 11 hours flight from Riyadh to Seoul i decided to return back to aircraft after few days.

On 12 Feb, I've made arrangement with Korea Business Airport Service (KBAS) representative, our ground handler for me to visit the aircraft to check the aircraft condition before our departure on 15th. This is a norm in VIP service as we don't want any surprise on departure date.

Miss Son from KBAS escort me to the aircraft from the terminal, security is very tight, the airport security did not allow me to bring my camera inside. Well no problem so we headed to the aircraft.

I've requested the maintenance support personnel to be there to assist me rectify the nose landing gear low extension problem. As per the maintenance manual, we are allowed to top up the nitrogen for the strut to bring it up to the specified length as per the chart in the MM as well as at the nose wheel well left hand bulkhead.

So i top up the nitrogen for the strut and got the required extension. Walkaround check found aircraft is in good condition. Headed back to the hotel after that.. long journey... 1 hr drive... no problem because they provide me nice big hyundai limo...

Thanks to Miss Son for the picture below, she shot it with her phone and email it to me.

Display Unit Goes Blank

I was preparing the aircraft for early morning departure and noticed the center upper DU goes blank. Aircaft is heading for Geneva and will fly back on the tonight.

I've reset the circuit breaker CB at P18 behind pilot seat nil joy, swapped it with lower center DU found defect transfered so confirmed the defect was the DU itself.

Check with Minimum Equipment List (MEL) found faulty lower DU is despatchable with cat C MEL.

My supervisor came onboard and double check the DU. He noticed a blink on the DU when he pull push the CB so he decided to do the ground test from FMC CDU maint page, walla.. sudddenly it come back to normal, so it is intermittent. However this is the sign that it gonna fail soon. So getting the spare in advance will be a good idea.

BBJ Winglet

Earlier BBJs was delivered without the winglet because it is still waiting for FAA approval. Now all BBJ delivered to customer with the winglet. Earlier BBJ have to go to winglet installation center like Patts Aviation in Wichita to get it installed, however nowadays there are few more maintenance organization approved by Boeing to carry out the installation like Malaysia Airlines Engineering in Kuala Lumpur.

Winglet mainly gave two major benefits, to reduce drag created by turbulence of airflow at the wing tip during flight thus provide fuel efficiency for longer flight range. Second benefit is cosmetic wise. It gave more corporate look for this VVIP aircraft. Imagine this BBJ without winglet, does it looks like corporate VIP aircraft? I don’t think so.

Below is the technical summary from Boeing website.

Blended winglets offer operational and economic benefits to BBJ and 737-800 customers. Mission block fuel is improved approximately 4 percent. Range capability is increased by as much as 200 nmi on the BBJ and 130 nmi on the 737-800 commercial airplane. The reduction in takeoff flap drag during the second segment of climb allows increased payload capability at takeoff-limited airports.
Environmental benefits include a 6.5 percent reduction in noise levels around airports on takeoff and a 4 percent reduction in nitrogen dioxide emissions on a 2,000-nmi flight.
The blended winglets now are available as standard equipment on BBJs, as optional equipment on 737-800 commercial airplanes, and by retrofit for BBJs, 737-800, and 737-700 commercial airplanes already in service. Because the winglet structure and systems follow established maintenance intervals and life cycles, winglets have a minimal effect on airplane maintenance.

Hydraulic Leaking

This happened 2 years ago but i still have the photo to share, massive hydraulic leaks around both main landing gear. Aircraft has been brought to maintenance facility for retraction test to confirmed the leak from main landing gear actuator however after 5 complete retaction cycle there is no sign of leak from either MLG actuator.

Here is the photo taken in Heathrow, after 8 hrs flight from base to pick-up VIP from London. It is difficult to make decision from where it leak when ground check unable to confirm it. Multiple theory was brought up by my work-mate such as it could be from ground spoiler, i'm insist on it is from the MLG even though ground check unable to confirm it.

Lucky for us the aircraft heading for hangar check and part of the package was to replaced the MLG actuator as called out by SB. Since then everything is back to normal so it prove that the culprit is the MLG actuator even though the ground retraction unable to proof it. Probably it need load from airflow when the aircraft take-off and approach to induce the leak.

What is BBJ?

I should put this as my first posting, not all know what BBJ is. Well it basically a glorified 737NG (next generation). NG series is -600/700/800/900. There is 2 type of BBJ, BBJ1 & BBJ2. BBJ1 basially a 737-700IGW (inreased grosss weight) due to it has a 737-700 fuselage with 737-800 wing's and center section so that's why IGW is there.

To cater for VIP needs for comfort (larger space onboard their private jet) plus longer range, Boeing with joint venture with General Electric has come out with the idea to sell this type of aircraft, BBJ1 in 1996 & BBJ2 in 1999. With additional fuel tanks in the cargo area, more fuel can be add up thus providing longer range. But of course it is give and take between range and payload. If you want more baggage space & more seats the range will be shorter than max fuel tanks in cargo with less passanger. For instance, max range with 8 vip onboard plus full fuel tanks can go up to 11,000km in range, basically from London to LA, Kuala Lumpur or Tokyo with ease.

The BBJ that came out from Boeing plant will be green aircraft ie without interior/cabin equipment. First it will be sent to Patts Aviation in Wichita, USA for auxiliary fuel tank installation. Depend on customer preference, the aux fuel tank which is basically like a cargo box will be installed in forward or aft cargo or maybe on both side. After that it will be sent to outfitting center furnish the cabin as per customer requirement. The very popular outfitter is Jet Aviation in Basel, Switzerland, very well known with their high quality workmanship.

After several months the aircraft will be delivered to their customer with their custom fit cabin. Sofas, full size bed (plus massage), showers, full size galley, big plasma TV with full surround sound, as per customer request, just name it but of course it will come with a price, not a problem if you are a billionaire.

Ayers Rock from 38000 ft.

All this while i was in impression that Ayers Rock is flat and round if to be seen from sky, until i personally see it from 38000 ft. As our flight route from Melbourne to Kuala Lumpur pass through Australian desert and so happen it was a day time, what an experience to see with my own eyes how this amazing natural thing looks like. As informed by our Australian captain, the Ayers Rock plays a significant role on aboriginies belief.

R/H Boost Pump Wire Burned.

Last week, mission from Riyadh to Melbourne, transit stop in Kuala Lumpur for 1 hr after 7 hrs flight. 2 hrs after airborne, the pilot called me to the cockpit and informed me that R/H aft boostpump Low Pressure light came on. As per crew checklist boost pump switch to be kept off.

Upon landing in Melbourne, noticed that the boost pump CB's in P62 PDP popped-out. Inspected the boost pump looks normal, however when i traced the wiring found burned wire about 1 ft from the pump itself. Defect put under MEL cat C, upon return to base, damaged wire repaired per Standard Wiring Practice Manual.

It is quite mysterious how the wires got burned, lightning strike? Landing was retracted as it happen 2 hrs after airborne. I noticed adjacent bolt to the burn area, probably arcing could be the caused.