Wolf

In yesterday’s post I asked about your most recent flight. Specifically, how did you, without checking your AFM first-segment climb gradient chart, know beyond the shadow of a doubt you were going to cross the departure end of the runway at a minimum of 35 feet.

The answer I was looking for is:

You did this when you determined your takeoff distance on the day, and checked to make sure you had at least that much runway. The number your AFM, QRH or perhaps your FMS gives you, guarantees you – as much as that is possible – that you will, in that distance, be able to either:

• accelerate and reject the takeoff if an engine failure occurs before V1,
• accelerate and continue the takeoff if an engine failure occurs at V1 – AND CROSS THE DEPARTURE END AT 35 feet, or,
• accelerate and continue the takeoff if no engine failure occurs – AND CROSS THE DEPARTURE END AT 35 feet.

In the last case, you’ll actually need less than the stated distance, because that gets “padded” by 15%.

You can read up on that in the FARs here.

Note that’s for a dry runway.

Next, I’ll talk more about the hurdles the departure procedure designers usually put in place to let us know what we have to do to be safe. Look for another post shortly but not immediately – I’m still working on the illustrations I’m gonna need.

Email b l o g @ e 6 b j e t . c o m if you have comments. I read them all, just can’t promise a reply. Please explicitly state if it’s okay for me to use your reply in future posts.

Cheers

My previous post had a 10-second video of a takeoff, and asked what happens right at the end of the video. A bit of a loaded question it was…

Note I will be talking about transport-category aircraft in this series. Those that are certified under FAR Part 25, or EASA CS-25. I’ll use the US regulations, but EASA’s are very similar.

The Answer

Here’s my answer. And another question, further down.

The gear having fully retracted and the doors closed, the aircraft reached the end of what is called the first segment in Aircraft Flight Manuals.

Some details about the first segment. Not hugely important.

Is this information about the first segment important? Well, in the grand scheme of all things Obstacle, not that much. But what is important is that you be able to answer the question down at the bottom of this post. And it might help with that.

You’ll have heard the term. Pilots tend to also remember that the first segment starts at lift-off, and that for two-engine aircraft, the climb gradient must only be positive *. And then try to forget what seems like unclear and worrisome knowledge.

In practical terms, that blue line in the diagram above has to be going up after lift-off and until the wheels are in the well. Though it doesn’t have to go up much.

Fictitious example: that twinjet of yours can do a 0.5% first-segment climb gradient. You’re taking off from a 5000-foot runway, lift off at the 2000-foot mark. Well, you’re gonna cross the departure end of the runway at 15 feet.

The folks who certified the airplane were happy with this. Are you? Probably not. There’s a different bunch of folks who design departure procedures for airports, and they have a completely different set of hurdles they want airplanes to overcome when taking off. And we have a vital interest in overcoming these.

The first requirement is usually that you’ve got to cross the departure end of the runway at a minimum of 35 feet. There’s more hurdles, but let’s do one thing at a time. Here’s the diagram again, with the designer’s first hurdle drawn in red.

The next question

So here’s the next question I’ll leave you to mull over for a while.

What did you do, before your most recent takeoff, to ensure that you could indeed make that first hurdle at 35 feet?

Allow me to highly doubt you pulled up your first-segment climb gradient charts, regular pilots don’t regularly do that.

Yet I’m sure you did check. How’d you do it?

My answer tomorrow.

• For three-engined aircraft the requirement is a bit better, the gradient must be a still-paltry 0.3%, and 0.5% if you have four engines. Technically, the first segment really starts when the aircraft reaches VLOF. Read up on it here, § 25.121 specifically.

Not the easiest topic, but I’ll give it a go. In bite-size chunks. I’ll do several posts on this, this is the first.

First, watch the 12-second video below, it’s a takeoff and initial climb from a chase position.

Then answer one question:

Something happens right at the end. But what?

Don’t watch it more than once or twice, you’re not looking for something tiny, subtle, or otherwise easy to miss.

The answer I’m looking for will be on my next post. That should be next Monday.

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This doesn’t always get the attention it deserves during training. The National Business Aircraft Association (NBAA) have done a superb job preparing an in-depth Pilot Briefing about it. Available as a PDF or as a Powerpoint document.

Go to NBAA.org Aircraft Operations – CNS – PBN and download from the Related Links sidebar on the right.

There are lots of detailed examples given for SIDs and STARs in the US. The Briefing also mentions the slight differences that apply in Canada. Invaluable for crews who aren’t in North America on a regular basis.

For the East side of the Pond, the UK CAA provides info on the topic, at SID-and-STAR-phraseology

See also Eurocontrol’s Phraseology Database, https://contentzone.eurocontrol.int/phraseology/

Shame there aren’t worked examples as in the NBAA Pilot Brief! An ounce of example is sometimes worth a pound of theory. Kudos, NBAA!