Ask Captain Lim ~ All about Aviation

Hi Captain Lim,

With reference to the question on the CAS and Mach, I am not again satisfied with it.

I referred to some documents and I found the answer.

The reason is that for a target CAS the TAS increases as you fly higher.
If the target CAS is 300 knots at MSL, then the TAs is also 300 knots.
As you fly higher the TAS would increase for same CAS. Also, as you fly higher
the Mach would decrease.

So for a target CAS of 300 knots, you would be flying super sonic if you fly at extreme
high altitudes.

So for a given target, CAS equivalent and Mach equivalent of TAS at a given altitude is same. This is called as crossover altitude. Up to this, they fly at CAS and after that they fly at Mach number.

This happens to be 31000 ft in your case.

I have further questions for you:-

1) Is the ETOPS Rules applicable to BRGA aircrafts? I see a lot of aircrafts like the Learjet, Canadair, etc which can fly non stop from London to NewYork. They are also twin jets. Do they also have to abide by the ETOPS Rules?

2) Do you have an ETOPS Chart, plotted for a particular route with the diversion time arcs from designated enroute alternates? I heard that every ETOPS pilot needs to carry that
for better monitoring. Could you give that and explain?

3) B777 is cleared for 180 Minutes ETOPS. So it can fly safely in single engine for 3 hours and land. Is this tested practically - for example, failing an engine and analyze whether it runs for 3 hours or more in air?

4) Have you ever flown a Boeing 777 in Single Engine? Please share your experiences?

5) I am trying to make a perfect landing using MSFS 2002. I perfectly capture the localizer and Glide Slope and maintain perfect speed. But just before landing, at, say 7-10 seconds before touch down, I see that the GS either move up or down. I think this happens when I flare the aircraft. I am never able to touch on markings nor keep GS at dead center. I have seen that some aircrafts like the B777 and B767 flare a lot and make a smooth touch down on the markings. Even the smoke appears to be very minimal.

Do you keep the GS exactly at the Center at the time of touch down? Please explain the key for a nice landing... the LAST 10 seconds!

Thanks and Warm regards

Srihari J

Hi Srihari,

Your previous question was, when CAS and Mach number are indicated in flight in the Boeing 777? The answer was when it crosses 31,000 feet. You have already researched the technical answers yourself regarding the speed relationship.

1. I believe all twin engine jets have to abide by ETOPs rules.

2. Yes, there are ETOPS and Enroute Alternate charts in all the Boeing 777's. Please read the details yourself as they are too lengthy for me to explain.

3. Of course, the180 minutes on single engine are tested by the engine manufacturers during the development stages otherwise it would not be certified by the relevant authorities to be used in passenger airplanes.

4. I have not flown on the Boeing 777 on single engine except in the simulator.

5. Flying a MSFS 2002 Simulator and the real airplane is not the same! I have mentioned in many FAQs that these MSFS simulator are good procedural trainers but the feel is totally different. You never manually fly a Boeing 777 ON THE INSTRUMENTS until touchdown! It would be too dangerous! As a general rule, most pilots fly on the ILS up to 200 feet above ground level on a Category 1 ILS and then fly visual below this height with the GS as a reference, but NEVER up to touch down, unless he is doing an Autoland. In an autoland, the landing is executed by the computer. For non-autoland, he must look out and land the airplane physically (without the help of the autopilot) below 200 feet. In the case of the MSFS, you got no choice but to fly the airplane to touchdown because there is no visual guidance outside. I have not flown a MSFS 2002 simulator and I cannot give you any guidance on how to fly it.

Hi Captain Lim,

Regarding 2nd question, I can read it but I do not have any chart. If you could send or upload one of the charts which u have used, that would be great.

Regarding the 4th question, I was pointing to MSFS but it was with reference to Boeing 777 only.

As you have said, you fly manually after 200 ft above ground level (agl). I have seen many videos where they make the full final approach manually, say from the point they capture LOC and GS.

You have LOC and GS so you can fly manually up to the decision height. After 200 agl, how do you manage to land at the dead center of the runway touchdown markings?

What is the secret to LAND exactly on the markings, even though you cannot see it?
Please let me know.

Thanks and warm regards,

Srihari J

Hi Srihari,

Sorry, I am unable to provide you the ETOPS charts.

It is true the ILS can be flown manually from the time the GS and LOC is captured on instrument. If an airfield is approved for a Category 1 ILS, you can legally fly to 200 feet agl only. Thereafter, you must look out and fly visually, NO MORE INSTRUMENT FLYING. If you can't see the Runway, you must go around! You CANNOT fly the GS and LOC on instrument until touch down as you would do in a MSFS simulator in your PC. I hope you understand this. If you are doing an Auto land approach, then it is a different story. The Autopilot, with the help the computers, could fly the airplane until touchdown safely, but not human beings in real life!