414 Epic E1000 N98FK Crash at Steamboat Springs: LNAV+V Advisory Glidepath Trap

Have you ever thought about how similar everything looks in the cockpit when you're flying

to LPV minimums versus to LNAV plus V minimums?

Think about it for a moment.

Literally, everything on the PFD is identical, except for inside VHSI, where in one case

you see small letters LPV, and in the other case you see LNAV plus V. And in both cases,

all of the needles are centered, and you get a reassuring picture that makes your brain

say, okay, we're good.

Yet, in one case you're perfectly safe, and in the other case you may fly into the

side of a mountain.

Today we're going to talk about the crash of November 9-8, Foxtrot Kilo, an epic E-1000,

the crash near Steamboat Springs, Colorado last week.

And like the DCA mid-air collision, I think it was an accident just waiting to happen.

The aircraft was flying an RNAV GPS approach with a plus V advisory glide path, which for

all the world looks like a normal GPS or ILS glide slope, except that it can take you

through terrain.

And we'll also talk about the three important criteria that must be met before you're

permitted to descend below an MDA.

And I'll talk about my experience flying this approach in a simulator and hitting the

same mountain.

Hello again and welcome to Aviation News Talk, where we talk in general aviation.

My name is Max Truscott.

I've been flying for 50 years on the author of several books in the 2008 National Flight

Instructor of the Year.

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Now let's dive into our main topic.

Today, we're talking about November 9-8, Foxtrot, Kilo, an epic E-1000, which crash

near Steamboats brings Colorado early on Friday morning.

And first, let me extend my condolences to the friends and family members who lost

loved ones in that crash.

It was truly a tragedy on them.

Sorry for those of you who lost loved ones.

And of course, the reason we talk about crashes is to try and help prevent future crashes.

As pilots, we can learn a lot from what happened in other accidents.

And so that's why we talk about these things.

Now it's early in the NTSB investigation, yet we already know much about what happened

from the ADSB data.

And the lessons we can learn are bigger than one airplane and one airport.

It's about something a lot of instrument pilots are a little fuzzy on, which is the

plus V that you sometimes see in the title of an approach, as you loaded into your avionics.

We'll talk later about advisory glide slopes, what they are, how to use them, and most

importantly, how not to use them so you don't get in trouble and possibly into an accident.

First, what I'm calling an advisory glide slope has many names.

Garmin calls it advisory vertical guidance, but they don't spend a lot of time explaining

it in their documentation.

You may also see it called an advisory glide path, because glide slopes are associated

with ILSs and glide paths are associated with R&F GPS approaches.

Since there are lots of names, I'll just pick one and continue to call it an advisory glide

slope, as that's what many pilots call it.

We'll get back to advisory glide slopes in a few minutes, but let's talk about the

accident.

First, let's talk about the airport environment.

Steamboat Springs, KSBS is surrounded by a high terrain, so if you don't follow every

instrument rule precisely and descend below minimums early, you may hit terrain.

And this accident is really useful as a teaching case, because so much of the approach was

flown correctly.

According to the ADSB track, the approach was flown nearly perfectly with one exception,

but in my opinion, the pilot likely thought that everything was okay and never realized

that he'd be hitting terrain.

Here's what we can see from the ADSB ground track and the barometric altitude data.

Laterally, meaning left and right, the aircraft was not wandering around.

It was tracking inbound in a course that closely matched the final course of the R&F GPS

Zulu Runway 3-2 approach.

But vertically, the aircraft ended up too low, too early, and hit terrain, even though

it was on the advisory glide slope.

Let's talk about the flight itself.

The aircraft departed KMKC, the Kansas City Downtown Airport, at 11 p.m. central time

on Thursday night.

According to a newspaper article, the purpose of the flight was for the aircraft owner to

take his two college-age sun skiing.

The flight lasted about two hours and twenty minutes, and would have arrived at Steamboat

Springs, Colorado at about twelve twenty a.m. mountain time.

The aircraft was a twenty twenty four epic E1000, which is a very capable six-place

turbo prop equipped with the latest version of the Garmin G1000, which is the NXI version.

That's the same version that's on the simulator that I used at my flight school to replicate

the aircraft's flight path.

I videotape that approach and have shared that video with listeners who support the

show via monthly donations via Patreon.

I make the video public at some point in the future, but if you want to see it now, sign

up to support the show at aviationnews.com slash Patreon.

The aircraft initially climbed to flight level two zero zero and later climbed to flight

level two four oh.

The Steamboat Springs Airport is located deep in a valley in the Rocky Mountains.

Its runway is four thousand four hundred fifty feet long, and the runways are three two

and one four.

The pilot had three instrument approaches to choose from, but because of terrain, none

was ideal with few options for a straight-in approach.

In addition, there was weather at the airport.

Twenty minutes before the accident, the weather was zero eight zero at six knots.

Visibility five, clouds scattered at two hundred feet, broken at twenty four hundred, overcast

at forty one hundred, and out timber three zero one five.

Two minutes before the accident, the ceilings had dropped.

The weather was calm, visibility ten, clouds scattered at five hundred feet, broke and

at sixteen hundred feet, overcast at twenty four hundred feet, and out timber three zero

one six.

So there were a number of risk factors that we often see in accidents, including fly

at night, in the mountains with weather.

First, let me talk about the two instrument approaches the pilot didn't choose.

One is the VOR DME Charlie approach.

The approach comes in from the south and then passes over the VOR, which is a located

2.9 miles south of the runway threshold.

The final approach course is 352, so it comes in at a 32 degree angle to runway three two.

The approach has only circling minimums, and the MDA is 8,140 feet, which is 1,250 feet

AGL.

Since the ceiling at the time was sixteen hundred broken, those minimums were 340 feet below

the clouds, so that approach normally could have worked.

But in the notes says the procedure is not authorized at night, so it was not an option.

The second approach is the Arnav GPS Echo.

It also comes in from the south.

However, unlike the VOR approach, which is straight with no bends, this approach follows

a valley and has a dog leg turnet pexa, which is the final approach fix.

Its final approach course is 323 degrees, which is the same alignment as the runway.

It also has the same MDA as the VOR approach of 8,140 feet.

And like the VOR approach, it has only circling minimums.

Why might you ask this approach, which is perfectly aligned with the runway, have only

circling minimums?

It turns out that's not unusual at mountain airports.

Circling only minimums are applied when the MDA is so high that an aircraft would need

a very steep descent gradient to get down to what might otherwise be a straightened

approach to a runway.

Specifically, if the descent angle is more than 3.77 degrees for C and C for a category

below, the approach cannot publish straightened minimums and will have circling minimums only.

For this approach, from the last fix waycore, which is just 2.2 nautical miles from the

runway threshold, an aircraft would need to drop 600 feet.

That would require a 7.75 degree glide path angle, which could result in an unstable approach.

So while you're allowed to land straight in, if you can get down that quickly, the Terps

rules don't permit listing straightened minimums because the FAA doesn't want to encourage

you to fly an approach with a high descent rate that might lead to an accident.

An aircraft flying this approach could easily circle to runway 1-4, though the notes say

that all circling must be to the southeast of the runway due to high terrain.

So this approach was a viable option.

The third approach, which the pilot apparently flew, is the Arnav GPS Zulu Runway 3-2 approach.

It's a relatively new approach created in 2024.

The Arnav Zulu has a final approach course of 340 degrees, which is a relatively straightened

approach to runway 3-2.

That makes it the only approach that steamboat springs with straightened minimums, which

may have been why the accident pilot chose it.

However, there are some gotchas.

The first is that it has higher minimums than the other approaches.

The approach has straightened L-nav minimums and circling minimums, which are identical,

9100 feet, which is a whopping 2219 feet AGL.

That's just 180 feet below the reported cloud layer when the pilot would have started

the approach, but it's well above the 1600 foot ceiling reported two minutes before

the accident.

So given this high MDA and the weather, the Arnav GPS Echo might have been a better choice

since its minimums were lower than the reported cloud heights.

Other gotchas for the approach can be found in the notes.

One is that runway 3-2 straightened minimums are not authorized at night.

Another note says circling runway 3-2-na at night.

So the pilot could not have legally landed on runway 3-2.

He would have had to circle to runway 1-4.

There is one other crucial note on the chart which goes to the heart of this accident,

and it's one that many pilots don't understand well, and that note differs depending upon

the type of instrument charts you use.

On the FAA government charts, the note simply says visual segment dash obstacles, and it's

not even in the normal notes section at the top of the chart.

Instead, it appears near the bottom of the chart at the top of the profile view or the

side view of the approach, so it would be easy to miss.

On the Jefferson charts, the note also appears in the profile view, and it says visual

segment dash obstacles, and below that it says, 34 colon 1 is not clear.

I'll talk more about these visual segment obstacle notes in a few minutes, but first

let's talk briefly about the requirements for descending below an MDA or minimum descent

altitude when flying a non-precision approach, and this is critical to understanding this accident.

After crossing the last fix, which is usually but not always the final approach fix, pilots

are permitted to descend to the MDA.

91.175c essentially says that you cannot descend below the MDA until all three of these

conditions are met.

One, the aircraft is continuously in a position from which it is sent to a landing on the intended

runway, can be made at a normal rate of descent using normal maneuvers, and for operations

conducted under part 121 or part 135, unless that descent rate will allow touchdown to occur

within the touchdown zone of the runway of intended landing.

Two, the flight visibility is not less than the visibility prescribed for the approach

being flown, and three, and this is critical.

You must have at least one of the visual references for the intended runway, distinctly

visible, and identifiable to the pilot, and there's a list of night items that include

things like the threshold, runway lights, marking, touchdown zone, vassier, papi, and

so on.

And if the approach lighting system is the only reference you have in view, you can't

descend below 100 feet above the touchdown zone elevation, unless the red terminating

bars or red side row bars are also distinctly visible and identifiable.

Now let's talk about the final phases of the accident flight.

I found the flight path data on ADSBXchange.com.

For the altitudes I'm going to mention, I added 240 feet to the altitude shown on ADSBXchange.com

to correct for non-standard pressure that was reported at the time of the accident as

30.16 inches.

It's clear from the ground track that the aircraft was vectored to a point where it could

be cleared to direct a tilly the IAF so that it had a turn of less than 90 degrees onto

the approach.

ADSB data shows that the aircraft was in altitude hold mode at 13,000 feet until it reached

tilly.

At tilly, the aircraft turned onto the approach and ADSB data shows that the autopilot's

approach mode was selected as the aircraft passed over tilly.

That would have allowed the autopilot to couple to the advisor glide slope of the approach.

Now we can't tell for sure from the data whether the autopilot actually coupled to the

advisor glide slope.

It's possible that the aircraft parallel the glide path by descending in vertical speed

mode.

Regardless, ADSB shows that the aircraft's descent angle was remarkably consistent from the

time it passed near tilly until it crashed.

Also, the descent angle did not change at all as the aircraft passed through the MDA,

so it's highly likely that the autopilot was coupled to the advisor glide slope.

Analysis of the data shows that the approach was flown very accurately.

It passed within .05 nautical miles of the final approach fix, MADKEE, so essentially overhead.

At MADKEE, the chart calls for the aircraft to be at or above 10,800 feet.

After correcting the altitude data, the aircraft appeared to across that fixed just 90 feet

high.

After the FAAF, there's one step down fix woodchuck.

That woodchuck the chart calls for the aircraft to be at or above 90,100 feet, which is

the MDA.

After correcting the altitude data, the aircraft appears to have crossed that fixed just 15 feet

high, so the approach was essentially perfectly flown.

At woodchuck, the aircraft was required to remain at or above the MDA until it had some

element of the runway in sight.

However, it's unlikely that the pilot had the runway in sight since there was a layer

of clouds over the airport, and also because there was a mountain ahead of the aircraft

that would have blocked any view of the airport.

So instead of leveling off the MDA, this aircraft continued descending through the MDA,

which is exactly what it would do if the autopilot was coupled to the advisory glide slope.

And that combines two common misconceptions.

One is that many pilots expect when flying an approach with an advisory glide slope,

the autopilot will level off at the MDA, but it won't.

Autopilot are designed to continue flying through minimums if they are coupled to a glide

slope of any type, including an advisory glide slope.

So to force the autopilot to level off, you need to either press the VS or a vertical

speed key sometime before reaching the MDA, or you need to press the Alt key or Altitude

hold key as you reach the MDA.

The other misconception is that many pilots think it's safe to continue descending below

the MDA if they stay on the advisory glide slope, but it is not.

In this case, the pilot remained on the advisory glide slope and hit the side of the mountain

because the advisory glide slope went through the terrain.

The last recorded data point was at 8,240 feet, which was 860 feet below the MDA.

Adjacent to the crash site, the top of Emerald Mountain is marked on the chart as having

an elevation of 8,250 feet or just 10 feet different.

Now I talked in detail about advisory glide slopes way back in episode 233, and I related

how a commercial student I was flying with had some of these common misconceptions I've

just discussed.

After I play that segment, I'm going to talk about how to identify obstacles in the visual

segments of an approach.

Here's what I said back in episode 233.

First, let's talk about advisory glide slopes, what they are, how to use them, and most

importantly, how not to use them so that they don't get you in trouble and possibly lead

to an accident.

The advisory vertical guidance, as Garmin calls it, is only found on Arnav approaches.

For most GA pilots, an Arnav approach means one that uses GPS.

Of course for some very capable aircraft, Arnav can use other sensors besides GPS, but

for most pilots, the Arnav approaches we fly use GPS.

So while advisory glide path might be a more accurate name, I'll continue to say advisory

glide slope is that's what most pilots call it.

Advisory glide slopes are found only on non-precision Arnav approaches, such as those with LNAV

or LP minimums.

So as we talk today about advisory glide slopes, we are not talking about approaches with

LPV and LNAV slash VNAV minimums.

Those are different in one very significant way.

Arnav approaches with LPV and LNAV slash VNAV minimums are essentially precision approaches.

So you are afforded protection as you descend along those glide paths down to the DA or

decision altitude, which is usually pretty close to the ground.

By contrast, on a non-precision Arnav approach, such as one with LNAV or LP minimums, an advisory

glide slope provides protection down to the MDA or minimum descent altitude, which is often

fairly high above the ground.

But there's no guarantee that you have any protection whatsoever along that advisory

glide slope after you descend below the MDA, hence the name advisory.

So why is it helpful to have an advisory glide slope on a non-precision approach?

Here's what I wrote in my Max Trust cuts, Garmin G3000 and G5000, Class Cockpit Handbook.

Historically, many instructors have taught students to dive and drive at each step of a

non-precision approach.

But the FAA has determined that the high descent rates used for this contributes to an increase

in accidents.

Hence the FAA now recommends stable descent rates be used on all non-precision approaches

and advisory glide slopes help pilots determine appropriate descent rates.

Note that dive and drive made sense on NDB approaches where you might have to look from

9 o'clock to 3 o'clock to find the airport.

But in a GPS world, the airport is usually at 12 o'clock and pilots no longer need to

rush down to midwims to get more time to search for an airport.

And from my Max Trust cuts GPS and Wass instrument flying handbook, in 2001, the FAA announced

that the industry should discontinue the use of a dive and drive process on non-precision

approaches since they contribute to see fit accidents, the leading cause of fatal commercial

air accidents worldwide.

Instead the FAA now advocates the use of procedures and training for a stabilized continuous descent

on non-precision approaches.

Some airlines have gone so far as to implement procedures that require pilots to immediately

initiate a missed approach if they don't see the airport when they reach the MDA, they

are not permitted to continue driving to the missed approach point.

Now to the best of my knowledge, advisory glide slopes are a garment invention.

And you'll see those advisory glide slopes on some approaches when using a garment navigator

such as the Garmin 43530, the GTN65750, or the Garmin G1000, 2000, 3000 or 5000.

Quoting again from my Max Trust cuts GPS and Wass instrument flying handbook, Garmin's

Wass capable receivers take away the guesswork on many approaches by providing an advisory

glide slope from the FAAF to the visual descent point, making it easy to fly a stabilized

approach.

Although the vertical guidance is strictly advisory, LNAV plus V can help make flying non-precision

approaches safer.

Unfortunately, it's not always easy to know ahead of time if an advisory glide slope

is available for a particular RNAV approach with LNAV minimums.

The easiest way to know if an advisory glide slope is available is to look at the approach

list displayed on your GPS when you select an approach.

LNAV plus V, or LP plus V, is shown next to non-precision approaches with advisory glide

slopes.

Otherwise, LNAV or LP is shown.

Jeppison charts indicate an advisory glide slope in the profile view with a dashed line

starting near the FAAF and terminating at the MDA.

From there, a dotted line continues to the runway threshold.

But the government FAA charts don't display advisory glide slopes, so you can't tell from

looking at them whether one is available.

Now, if that sounds odd, remember that advisory glide slopes are not present in the physical

sense.

They're just creations of a GPS receiver's microprocessor, its database of points, and the firmware

that provides instructions to the microprocessor.

Traditionally, glide slopes refer to an ILS using two transmitters and ground-based directional

antennas that sent precise radio signals into the air that pilots follow.

For RNAV GPS approaches, flown with a was capable receiver, no glide slope is transmitted

from the ground.

Instead, the receiver calculates target altitudes for every point along a GPS approach, provided

of course that vertical data was created for a particular approach and inserted into

the receiver database.

Using GPS satellites in the was infrastructure, a receiver determines an aircraft's present

altitude, calculates the difference between it and the desired target altitude, and displays

that difference on the vertical deviation indicator and on the CDI.

As you've probably surmised, vertical data for all approaches with LPV and LNAV slash

VNAV minimums is contained in was capable receiver databases.

Without it, these approaches wouldn't exist, however there is no requirement for vertical

data for LNAV or LP approaches, so advisory glide slopes don't exist for all approaches.

Now, by the way, was based vertical guidance does not terminate at the MDA or DA, which

makes it consistent with how expensive flight management systems work.

Typically, the vertical path starts at the FAAF and extends to either the missed approach

point or to 50 feet above the runway where vertical guidance ceases.

The signal is shut off at 50 feet AGL to prevent pilots from attempting to fly a was signal

down to the surface in zero-zero conditions.

The vertical path can also start after the FAAF.

If a path starting at the FAAF would descend below the minimum altitude required for a subsequent

step down fix.

Typically a three degree glide path is generated however it differs on some approaches to accommodate

obstacles.

In note that LNAV approaches provide the same obstacle protection below the MDA, regardless

of whether they have an advisory glide slope.

Do not become complacent simply because an advisory glide slope exists.

So just to summarize, some approaches with LNAV or LPV minimums have an advisory glide

slope you can display on a Garmin Navigator.

When it exists, you'll see it in the Garmin Navigator when you go to load an approach by

pressing the PROC key.

If you're given a choice that says LNAV or LP, now there's no advisory glide slope.

If you're given a choice that says LNAV plus V or LP plus V, then there is an advisory glide

slope.

After you've loaded an approach with an advisory glide slope, if you push the FPL key

to open the flight plan, you'll notice that the white line of text that precedes the

instrument approach includes either LNAV plus V or LP plus V in the title of the approach.

Later as you pass the intermediate fix, you'll see either LNAV plus V or LP plus V,

unseated in the HSI if you're flying a Garmin G1000, 2000, 3000 or 5000, or if you're using

a Garmin 43530 or GTN65750, you'll see it unseated on the Navigator.

It is safe to follow the advisory glide slope to the MDA, but there are no guarantees

that it's safe to follow it below the MDA.

And just to give you a real life example, last week I flew a night cross country flight

with a client from Palo Alto to Pasa Robles, which is about 130 miles away, so that he

could meet one of the requirements for the commercial checkride, which is a two hour, 100

nautical mile, night cross country.

Since it's very dark around the Pasa Robles Airport, we decided to fly the RNAV GPS

3-1 there to provide an additional measure of safety as we landed at the airport.

The RNAV 3-1 has only LNAV minimums, but it has an advisory glide slope.

We follow the advisory glide slope to 1400 feet, which is the MDA, and the pilot city plant

to follow the advisory glide slope below the MDA to the runway.

I told him, no, we should continue flying level at the MDA until we saw the Vasi or Pappy

and follow it to the ground.

That's what we did and the Pappy kept us somewhat above the advisory glide slope.

Would it have been safe to fly the advisory glide slope instead?

Perhaps.

But we had no guarantee that it would be safe, which is why below the MDA we waited and

used the Pappy to guide us instead.

Now let's talk a little more about the visual segment obstacle notes.

Specifically, I want you to be able to tell when you look at an instrument approach chart,

whether there are any obstacles below the MDA.

And sadly, the clues to the presence of obstacles are subtle and easily missed by pilots.

And as we can see from this accident, it's very important that you determine whether

any obstacles exist, particularly if you're flying into an unfamiliar airport at night.

First, why is it called the visual segment?

Well, you are only permitted to send below the MDA when you have some element of the

runway in sight.

So from the MDA down to the runway is a visual segment.

You must have the runway continuously in sight anytime you are below the MDA.

You cannot just follow the advisory glide slope below the MDA unless you also have the

runway in sight.

To evaluate the visual area, the FAA examines obstacles along this path and whether they

protrude up through two artificial surfaces that extend outward from the runway.

These surfaces are in client planes that begin 200 feet from the runway threshold and extend

back down the approach toward the decision altitude point for approaches with vertical

guidance or to the VDP, the visual descent point for non-precision approaches and back

to 10,000 feet when evaluating for a circling approach.

Now one of these surfaces is called the 34 to 1 surface, which represents about a 1.7

degree angle.

So this surface is about half the 3 degree angle that aircraft typically follow on an

instrument approach.

If an obstacle penetrates this surface, then we'll see the same notes that are found

on the RNAV GPS Zulu 3-2 approach and esteem broke springs.

On the FAA charts we'll see the words, visual segment obstacles and a jeps and charts

we'll see the words, visual segment obstacles and below that it says 34 to 1 is not clear.

Those notes are frankly way too subtle and easily missed, I think most pilots when reading

those notes would never think, oh, there could be a mountain in front of me that I'll

hit if I stay on the advisory glide slope.

Yeah, that is exactly the kind of thing you should be thinking when you read those notes.

There's also something that's even more subtle to indicate whether the visual segment

is clear of obstacles.

This comes from the instrument procedure's handbook, it says quote, for RNAV approaches

only, the presence of a gray shaded line from the MDA to the runway symbol in the profile

view is an indication that the visual segment below the MDA is clear of obstructions on

the 34 to 1 slope.

Absence of that gray shaded area indicates the 34 to 1 OCS is not free of obstructions.

So it's the absence of a gray shaded area, an area that you probably haven't paid much

attention to before, tells you that there could be a mountain right in front of you.

Now there's also a 21 surface for evaluating obstacles, and the switch should really

scare you, as it has an angle of 2.86 degrees, or essentially the same as the 3-degree angle

used for most instrument approaches.

Again, quoting from the instrument procedure's handbook, when the 21 surface is penetrated

by an obstacle, there will be a note on the chart prohibiting approaches to the affected

runway at night, both straight in and circling.

Maybe permitted at night, if penetrating obstacles are marked and lighted.

If the penetrating obstacles are not marked and lighted, a note is published that night

circling is not authorized.

So don't even think about flying an approach that is not authorized at night, as those

obstacles might be right up next to your approach path.

By the way, there is one other element of this accident we haven't discussed, and that

is that the Arnav GPS Zulu runaway 3-2 approach has only category A and B minimums.

Category B minimums would permit an aircraft to fly the approach it up to 120 knots, but

not faster than that.

The accident aircraft was flying considerably faster than 120 knots, however that fact did

not in any way change the outcome.

It appears that this crash would have occurred at any speed the aircraft might have been flying.

Now let me talk briefly about simulators.

There is huge value to having access to a simulator and using it to fly approaches

before you get into the airplane and fly to an unfamiliar airport.

One listener once told me that he flies for a company that has one or more vision jets

and that the company bought a simulator so that the pilots could do just that, and you

learn so much from flying an approach in a simulator before you have to do it for real

in an airplane.

Now I flew this particular approach into steamboat springs in our flight school simulator,

and it couldn't have been more obvious that if we followed the advisory glide slope

below the MDA that we would fly into the side of a mountain.

Interestingly, I had thought that having the relative terrain displayed on the moving

map would have given me sufficient warning that I was about to fly into a mountain, but

on this approach it didn't.

The relative terrain feature uses colors on the moving map to show whether nearby terrain

is above or below you.

In most garment glass cockpits, red shows that terrain is either above you or as little

as a hundred feet below you.

Yellow shows you that terrain is between a hundred feet and a thousand feet below you.

In green shows you that terrain is between a thousand feet and two thousand feet below

you.

Now I've never liked that yellow is defined as one hundred feet to one thousand feet

below you, because if the terrain is a thousand feet below you, well you're quite safe.

But if it's only one hundred feet below you, you are in imminent danger.

So when you see a yellow on one of these moving maps, you really don't know if you're safe

or in danger.

Now I think a better depiction is what was used in WingX, which was an electronic flight

bag that I used before for flight was introduced in fact long before iPhones became available.

In WingX, as I recall, yellow was for terrain that was five hundred feet to one thousand

feet below you.

So with that depiction, yellow was relatively safe all the time.

When I flew this approach in the simulator, I had relative terrain displayed, and as I

approached the mountaintop, I could see the yellow area getting larger and larger as I

descended toward the mountain.

But I didn't recall that area turning red.

After reviewing the video that I shot, I saw that it started turning red just nine seconds

before impact.

And frankly, that's not enough time for a pilot to notice it and react, especially if

they happen to be looking at something else at the time.

So while I rely heavily on relative terrain for safety when I fly especially at night,

I make sure it's always turned on at night.

It reinforced to me that pilots should always treat yellow as danger unless they have specific

knowledge about the terrain in that area.

And by the way, you don't need a full simulator to test fly this approach.

Patreon mega supporter Ed Carroll's emailed me soon after the accident in the road and

part.

In for flight, if you look at the 3D preview of the flight from the map page, FPL pane,

the globe icon left of edit slash nav log slash profile.

The 3D depiction seems to follow this glide path from map key to the runway, and it intersects

the terrain right where this crash occurred.

I think this 3D depiction really drives home the importance of understanding the approach

profile rather than just following a line on the profile pane.

And Ed attached a screenshot from for flight in which the aircraft path disappears as it

goes through terrain and then reappears on the other side of the mountain and continues

to the airport.

Very, very sobering.

And it shows how easy it is for pilots to check an advisory glide slope against the terrain

before they fly.

Now I want to bring us back to what I said at the very beginning of this episode, which

is that unfortunately everything in the cockpit looks virtually identical, whether you're

flying to LPV minimums or to LNAV plus V minimums.

It's unfortunate that an advisory glide slope is depicted exactly the same as a GPS glide

path, the same diamond, the same magenta color.

And flying an advisory glide slope, there is literally nothing on the PFD that screams

out to you that once you go below the MDA, you may fly into the side of a mountain.

The only thing that tells you this is the letters LNAV plus V versus the letters LPV inside

the HSI.

It's easy to miss those letters.

And even if you see them, many pilots don't know that an advisory glide path is only

safe to fly above the MDA, and that it affords zero protection below the MDA.

Now that should be very sobering to you, and I hope it's a wake up call to aircraft

and avionics manufacturers.

Yes, pilots need to know that flying an advisory glide slope below the MDA might not be safe.

But they shouldn't die just because they don't know those facts.

There should be some kind of change at the MDA, some kind of warning to let pilots know

that the advisory glide slope that brought them safely to the MDA can no longer be trusted

below the MDA.

The PFD shouldn't look identical except for those letters LPV or LNAV plus V. That may

be adequate information for professional pilots who fly for a living, but it's way too

subtle a difference for weekend warriors who don't fly for a living.

So what can we take away from this accident?

Well, the first is that instrument flying is hard, and that it's very unforgiving.

There are many subtle details involved in flying instrument approaches.

If most of your flying is in relatively flat country, then overlooking some of those details

won't necessarily cause a crash.

But flying in the mountains is very unforgiving.

You have to pay attention to all of the details, and you have to understand all of the

notes on an instrument chart.

As I've told many clients, when you're doing something that could kill you, such as

flying, you want to learn everything about it that you can, and no detail is too small.

You must understand the difference between a DA on a precision approach and the MDA on

a not precision approach.

With a DA, when you reach the decision altitude, you must make a decision to either land or

go around.

With an MDA, when you reach that minimum descent altitude, you must level off unless you

have some portion of the runway in sight.

And having an advisory glide slope does not change either of those rules, and the fact that

an autopilot will continue to descend on an advisory glide slope and won't level off,

and it will take you right through the MDA, that too doesn't change those rules.

You have to understand that you must level off at an MDA, and you have to understand that

once you go below the MDA, the presence of an advisory glide slope doesn't mean that

it's safe to descend.

You may in fact hit an obstacle, even when you're on the advisory glide slope, and you

can only go below the MDA if you have the runway in sight.

If you've learned something from this episode, please consider making a donation to support

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So until next time, fly safely, have fun and keep the blue side up, and remember that

you can always go around.

If it don't look right, coming down, don't wait until you're silent, baby, sliding

upside down, you can always go around.