Primary Pitch Instrument on ILS


#1

This is a good discussion point for those of you that are working towards your instrument rating, as well as those of you CFII’s that are doing the teaching.

As a CFI/CFII/MEI, I often see other instructors teaching students that the Primary for Pitch on an ILS approach (glideslope) is the VSI. These students are often getting confused when taking their oral, because in one sense they rely on the GSI (glideslope indicator) as primary for pitch when flying the approach… while in the exam room they state that the primary for pitch (as they have been taught) is the VSI. Thankfully most examiners are not failing them for this misconception, but it does eliminate confusion in the minds of our students by giving them the correct understanding along with the right information. The primary for pitch IS the glideslope indicator…the reason it is not the VSI is because the vertical speed indicator does not take groundspeed changes into account.

Just a little issue, but it may help eliminate some confusion:)


#2

Wow! I didn’t know that. I’m not a pilot (yet), but I fly a computer flight simulator, FligthGear (It’s totally free and the quality on some things is as good as FS(flightgear.org)) and ALWAYS use the GSI when shooting an ILS APP. The VSI is delayed 6-9 seconds so it’s not very useful for monitoring pitch on a GS. You should talk to cfijames, he is a CFI. His father (here to make sure he doesn’t get out of hand :laughing: ) is JHEM.


#3

Yup, I’m here.
In the Pilatus, the VSI will read much higher on a standard ILS than it would read if I were flying in a 172. Same goes (as correctly stated above) for groundspeed changes due to wind. With a massive headwind, the pilot will need to carry extra power to keep the plane on glide path, and the VSI will show an appropriately reduced rate of decent. Same goes for tailwinds, more aggressive decent rates are required.
Thing to remember is that the glide slope is fixed in space, the RATE of decent is dependant on TIME. If you’re going faster or slower, it will take you less or more time to travel the same distance, i.e. from the Final Approach fix to the DH, and the pilot will have to increase of decrease the rate to stay on glide.


#4

Hey James…thanks for the input. Good to see that there are other instructors out there that are teaching things correctly. As you mentioned from flying the PC-12…there is a huge difference in your rate of descent when flying faster aircraft. I fly charter when I am not instructing (instructing is my pastime) and have time in the Hawker 800 XP as well as the Lear 35/J. The difference is exponential in the Lear…Vref at 138 (depending on weight obviously) means a descent rate that puts 172s and Archers to shame.

By the way, how does that PC-12 handle? I have no time in that type, but I’ve heard its about like flying the CJ-2…is that assumption correct?


#5

I have about 15 hours in a CJ2, but it was very informal and I never got to land it myself, so I really cant compare.
The PC12/45 is very heavy in roll. It really takes some muscle to get it started into a bank, but Ive gotten used to it. Once in the turn it will just stay right there, it’s very neutral.
The PC12/47 as, stated in numerous articles in the press, is much lighter in roll forces. It feels like a much lighter plane, and the first few flights it takes some getting used to.
Crosswinds are cake. The /47 has different winglets, supposedly to improve cruise as well as crosswind handling, but I havent noticed any difference.
Trailing-Link gear and large, low pressure tires (as well as exceptional flying abilities:wink: ) make for very smooth landings.
-J-


#6

Nice…

The “yoke actuator” always plays a critical role in how aircraft fly…LOL

The Lear is very solid, but tends to have some rolling tendencies (thanks to the tip tanks). The Hawker on the other hand is very forgiving, and has very good landing characteristics (along with some good pilot skill of course).