Archive for aircraft maintenance

Air Travel Delays: “Mechanical Issues”

Posted in air travel, air traveler, aircraft maintenance, airline, airline cartoon, airline delays, airline industry, airline passenger, airline pilot, airline pilot blog, airline safety, airliner, fear of flying, flight, flight attendant, flight crew, flight delays, FoF, passenger with tags , , , , , , , on April 21, 2018 by Chris Manno


“Mechanical issues” may sound like a catch-all for airline delays or, to anxious flyers, a mysterious, perhaps worrisome possibility. But it’s neither, and here’s why.

First, you have to understand two main concepts: airliners are complex mechanical wonders, and second, their maintenance and operation is very strictly and minutely regulated–and documented. This second point is essential to the aviation regulatory standard upheld by all major airlines, even though such detail must be correctly, diligently accomplished. That takes time. So, let’s walk through the possibilities.

air FA smile 001

When you board an airliner, preflight checks are ongoing. This is especially true if the aircraft has just arrived from another station (airport). As soon as the flight completion checklists are accomplished, the preflight process begins anew by the crew. To waste no time, this preflight inspection goes on even as arriving passengers deplane and departing passengers board.

The checks ensure that all operating systems on the aircraft are up to the very specific standard set by the aviation regulatory agency that oversees commercial flight operations. In the United States, that’s the Federal Aviation Administration (FAA).

Every system on that aircraft has an operational standard to determine if the aircraft is airworthy, and the jet does not move until those requirements are satisfied, right down to individual light bulbs.

Let’s look at that example: a light bulb.

If a pilot on an exterior preflight notices say, a landing light that is not working, this fact is immediately recorded in the aircraft logbook and the airline’s maintenance center is notified. The airline maintenance center will refer to the FAA specified “Minimum Equipment List” (MEL) for that particular aircraft.


Without straying too deeply into the very complex decision tree of the MEL, there are three possible outcomes for the noted discrepancy (a landing light is inoperative). First, the landing light may be replaced, tested and certified by an FAA licensed and approved aircraft maintenance technician.

Second, the item may be specified by the FAA-approved MEL as non-essential for flight under specified conditions. For example, if the aircraft is about to depart for a destination to land in daylight, the MEL may allow the flight to depart, with proper logbook documentation of the exception.

Third, the MEL may allow for a redundant system to compensate for the component. If the inoperative bulb was a wingtip position light, the MEL may allow the flight to operate with the remaining position light–if the aircraft has two and only one is required (that’s why the aircraft designer put two bulbs there in the first place).

This is the same with all aircraft systems: if there are redundant systems approved by the FAA MEL, the flight may be approved for flight with that waiver to use the backup system, once the discrepancy and waiver are properly documented in the aircraft logbook.

Of course, some essential systems have no redundancy. In those cases, prescribed repairs must be made by FAA-certified mechanics (example: a tire at the prescribed wear limit must be replaced). The discrepancy, repair and results must be properly documented before the aircraft moves.

And there are “consumables.” For example, on my flight last night, when we were doing our “Before Landing Checklist,” we noted that the engine oil quantity was at the prescribed “refill” level. That, like all aircraft specifications, is a very conservative number. It’s as if you were driving your car down the highway and noted that you had just above a half a tank of gas.

air airliner drive 001

You’d turn to your passengers and say, “The MEL says we must always have more than a half a tank of gas, so we’re going to exit the freeway and refuel now.”

In flight, I sent a data-linked message to our technical operations center noting the requirement for oil service before the next flight, which I also wrote in the aircraft’s paper logbook.

Our tech folks coordinated with the mechanics at our destination to have the oil ready and a certified mechanic to perform the refill. That’s quick and easy at one of our hub airports, because we have mechanics on staff there.

At smaller stations, airlines rely of FAA-licensed mechanics approved for contract mechanical work on specified aircraft. Of course, most airlines have access to normal consumables like oil or tires, but no one has every part on every aircraft stocked at every station.

route map NWA

If the required item is not in stock, it must be brought in, either from nearby (example: an airline’s LAX station may have an item needed for a flight out of Ontario Airport; staff can simply drive the part from Los Angeles International to Ontario). Other parts may be flown in on the next aircraft from the hub to the smaller station.

But either way, before the aircraft flies again, the prescribed maintenance procedure must be accomplished in accordance with FAA regulations and everything must be documented.

Most major airlines have this process streamlined for efficiency, like when I sent the data-linked message to prepare the arrival station for the required oil service. This was accomplished between flights with no delay. The certified mechanic noted the refill quantity and manufacturer’s details in the aircraft logbook as well as in the computerized records maintained at our airline technical headquarters.

But sometimes a procedure may take longer just by the normal time the process requires (changing a tire will take longer than changing a light bulb). Finally, the availability of mechanics at a given hour may add more time to the required procedure.

In all cases, the aircraft records must be meticulously documented, which takes time as well: approvals must be granted, remedial actions certified, and everything recorded both in the aircraft on-board paper logbook as well as the aircraft records at the airline’s technical center.

That takes time.

If the delay is predicted to be too long, we might be assigned another aircraft for the flight, which also takes time: passengers, cargo, baggage, and catering must be transferred to the new aircraft. So, if you’re waiting on board during a maintenance delay, it’s probably because swapping aircraft would take longer, or there isn’t another aircraft available.

To summarize, airliners today are complex machines with multiple parts and systems, all of which have MEL specified operating minimums. Not all replacement items are available system-wide, and and even where mechanics are immediately available, remedial processes can take time.

The “mechanical delay” we experience is due to the airlines’ unwavering adherence to very specific FAA standards.

The good news is, that’s why air travel on major airlines is as reliably safe as it is.









Fly early, or be late.

Posted in air travel, aircraft maintenance, airline delays, airline ticket prices, airliner, airlines, airport, flight attendant, flight crew, flight delays, jet, passenger, travel, travel tips, Uncategorized with tags , , , , , , , , , , , , , , , , on February 27, 2010 by Chris Manno

Fly early, or be late. Here’s why.

First, consider aircraft and crew access. On the first few flights of the day, both the aircraft and crew are beginning their first flight of the day. That’s important to you, because it means they most likely spent the night at the airport. So when you get there, they’re already at the gate, not coming in from a distant location, subject to arrival delays due to weather.

Some important advantages you gain early in the day:

1. If on the last flight the aircraft had any mechanical discrepancies reported, mechanics have had all night to perform any required maintenance.

2. The crew, too, is fresh: their FAA mandated maximum day is just starting. No problems with crew legalities.

3. The crew is together–not the cabin crew coming in from one coast, the flight deck crew from the other. They’re all starting from this particular airport.

4. The maintenance shift has just begun, plenty of time for mechanics to complete any work before shift change. More about that later.

5. Less gate delays: the aircraft is likely ON the gate, not waiting for the gate to become available, thereby delaying their deplaning, your boarding, and the swap of cargo and baggage.

Delays due to crew manning, maintenance requirements, and gate availability are much less likely EARLY IN THE DAY.

Next, think about passenger loads, because they do affect you. Here’s a chart of planned departure times and passenger loads from Denver to Chicago on one air carrier:

Passenger Loads Denver to O’Hare 2-27-10

Flight Departs Arrives Passengers Capacity
1 0700 0914 65 148
2 0755 1008 71 148
3 0845 1100 110 148
4 0955 1215 127 148
5 1100 1300 165 172
6 1135 1345 138 148
7 1210 1430 142 148
8 1255 1520 144 148
9 1340 1605 255 237
10 1450 1720 150 148
11 1535 1755 181 178
12 1650 1917 155 148
13 1800 2005 135 148
14 1900 2110 142 148
15 1950 2205 128 148
16 2055 2305 101 148
17 2130 2350 65 148

Note that before noon, the flights aren’t quite booked full, but after noon, several are overbooked. Why?

If you’re early, particularly in a mid-continent hub like Denver, DFW or Chicago, no one has been able to fly in yet to connect: the east coast flights haven’t landed yet, and the west coast, hours behind, haven’t even begun to board and dispatch. Which means less competition for seats with standby upgrades or overbooking.

But you’re not standby, you say, right? You will be if there’s a cancellation, especially of your flight. But look at the above chart–your best bet to snag another seat is in the morning. By the afternoon, a bow wave of standby passengers will have those flights packed to the gills.

Once the connecting flights from either coast or commuter connections from outlying areas add their passengers into the hub airport passenger pool, it’s a whole different ballgame. If arrival at your destination is time critical, or if you have a down-line connection the odds are more in your favor early in the day. Later, as the day goes on and delays, cancellations and stand-by lists begin to snowball, not so much.

Here are two other crucial factors that can be largely sidestepped early in the day.

1. Weather.

Sure, there are storms in the morning sometimes. But not the ones that result from the day’s heating and convection of moisture. But even if there is bad weather in the morning, if your aircraft is on its first flight of the day, at least it’s there–and so is your crew. Later in the day, your inbound jet could have to divert because of weather, tossing you into the standby line, or inducing a large delay. Crews, too, start running up against the FAA duty limits due to diversions. Don’t gripe–the FAA limits are for your protection as well as mine: you really want me on duty more than 14 hours for your landing?

2. Maintenance shift change. Why is this important? Simple: because an FAA-certified mechanic is performing licensed procedures on any aircraft. His signature goes on the paperwork certifying the maintenance action. It’s just not workable for one mechanic to do part of the procedure, then have another finish and sign for the entire job. So, if the first flights are at 6:00 or 7:00 in the morning, add eight hours and see when lengthy maintenance actions will probably not be started because they can’t be finished within the shift and so are likely to wait for the next shift. Which means you will wait, too. And I know what you’re thinking, but no–there’s no money for mechanics’ overtime in the sea of red ink flowing from the airline industry. The job will be done right, but you’ll likely wait.

Finally, I recommend you board early. That’s because of human nature: nobody’s going to do as they’re told and put one of their hand-carried items under their seat, then maybe one in the overhead storage bin. If you board last, it’s likely to be you standing in the aisle with a bag but no place to put it.

Other passengers will avoid eye contact with you, acting as if they DIDN’T already hog all the overhead storage space–but they did. And your bag is going to have to be gate-checked, whether you want it to or not. Choose a seat near the mid-point of the cabin if you can, which means the middle boarding call:

I like those emergency exits over the wing. Not only is there more leg room,  it’s also the smoothest ride  because the center of gravity and thus the pivot point of the jet in both pitch and roll are there. No, you won’t see much on the ground because the wing is in the way, but  you also won’t be the last group called to board, and thus be stuck with nowhere to stow your hand-carried items. You also won’t have to wait for the entire aircraft to deplane before you can get off–you’ll be in the middle of the pack.

Okay, got all that? Here’s a summary: early, early, early; booking, boarding, flying. You’ll have a smoother flight with less opportunity for delays.

Good luck, and by the way, don’t look for me at the airport when you get there early: I’m not an early morning person. Since the plane won’t leave without me, I’ll take my chances later.

Lake Tahoe


Sure, it’s always funny till someone loses an eye.


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