Bug report list part 4

[Tom Knudsen]

The list is getting smaller 

1. Transponder selector is set to TA/RA at default cold & dark 

- is this normal?

I guess this will be catched on the checklist item "Radios, radar and transponder" but I think it is strange it is not in standby on ground initial startup unless some pilots have left it on

2. VNAV Descent Speed is 6000+ feet per minute on descent

- Had to manually overide this as I think passengers would scream  a bit

If not a bug, when would the passenger start to scream (not that I want them to, but good to know the limits )

Normally I do a level-change or in many cases a V/S speed between 2200-2600 depending on the profile, but I like to calculate

Altitude current - Altitude scheduled times 3 = Descent rate

So i.e. FL300 down to FL100 = 30000 feet which becomes 30 x 3 +5 for extra safety = So I need to start decent 65nm from the waypoint I want to be at FL100

This gives me an descent rate of about 2200

As you can see from this image the airplane chose to expedite the descent rate on LVL CHG

 

 

Successful flight, so no logs are needed to include.

 

[Cameron]

You should have included a debug log for this flight. That would allow us to generate a vnav profile and understand the step descent.

[mmerelles]

1 hour ago, Tom Knudsen said:

The list is getting smaller 

1. Transponder selector is set to TA/RA at default cold & dark 

- is this normal?

I guess this will be catched on the checklist item "Radios, radar and transponder" but I think it is strange it is not in standby on ground initial startup unless some pilots have left it on

2. VNAV Descent Speed is 6000+ feet per minute on descent

- Had to manually overide this as I think passengers would scream  a bit

If not a bug, when would the passenger start to scream (not that I want them to, but good to know the limits )

Normally I do a level-change or in many cases a V/S speed between 2200-2600 depending on the profile, but I like to calculate

Altitude current - Altitude scheduled times 3 = Descent rate

So i.e. FL300 down to FL100 = 30000 feet which becomes 30 x 3 +5 for extra safety = So I need to start decent 65nm from the waypoint I want to be at FL100

This gives me an descent rate of about 2200

As you can see from this image the airplane chose to expedite the descent rate on LVL CHG

 

 

Successful flight, so no logs are needed to include.

 

 

watch your IAS target .84, the aircraft is pointing the nose way down to increase its speed to .84. this is a known bug.

 

When you clic FLCH the aircraft should keep its speed and because throttles are retarded to idle it should put the nose down a bit to mantain its present speed. BUT when you press FLCH the speed re-sets to .84 MAC (due to the bug) and the aircraft dives down like crazy trying to reach target speed.

 

edit: forgot to say, workaround is press FLCH and immediately reconfigure IAS target as per your present speed to have a nice FLCH descend rate

Edited May 6, 2016 by mmerelles

[Ubbi]

And you operate the Transponder with the standby-auto-off switch on the right side of the transponder. If it is set to AUTO like in your shot, the transponder will only start working if airborne...

[Tom Knudsen]

And you operate the Transponder with the standby-auto-off switch on the right side of the transponder. If it is set to AUTO like in your shot, the transponder will only start working if airborne...

Thanks but I know how the transponder works

[JRBarrett]

Thanks but I know how the transponder works [emoji6]

Some additional background on the TA/RA switch. (I am an avionics tech for a corporate jet operator).

As long as the transponder is in "standby" mode on the ground, it is OK to leave the TCAS set to TA/RA. The TCAS processor is a separate unit from the ATC transponder. It has two directional receiving antennas - one on top of the fuselage, and one below.

These antennas receive signals from the transponders of other other aircraft in flight, and the TCAS calculates the bearing, distance and relative altitude of airborne targets.

The TCAS has no transmitting ability on its own. In order to send interrogations to other aircraft (known as "squitter"), the TCAS uses the transmitter portion of the aircraft's transponder as its link to the outside world. As long as the transponder is selected to standby (either manually, or automatically via weight-on-wheels sensors), the TCAS cannot transmit.

In years past, it was always standard practice to place an aircraft's transponder in STBY mode as soon as exiting the runway after landing, and to not turn it on until entering the runway for takeoff.

Now, however, many large airports with heavy traffic volumes are equipped with surface detection radar known as ASDE-X, which permits ground controllers to see the exact positions of taxiing aircraft, even at night or in conditions of poor visibility. At such airports, all aircraft moving on taxiways are required to turn their transponders "on", so ground controllers can see them on ASDE-X.

In this situation, the pilot should turn the TCAS to STBY or OFF, to prevent it from sending squitter interrogations through the transponder, which could cause false TCAS alerts in other aircraft which are in the process of taking off or approaching for landing.

Many aircraft are equipped with ATC control panels which combine both TCAS and transponder control in a single rotary knob - with transponder modes coming first, followed by TCAS modes.

The control panel emulated in the IXEG 737 is one in which the transponder and TCAS mode selectors are separate.

[Litjan]

Thanks gentlemen, nothing for me to add here. And thanks again for the report, Tom - especially the .84 issue should be fixed in 1.0.3 - the autopilot will now retain the current commanded speed when switching from VNAV to another pitch mode.

Jan

 

[Tom Knudsen]

7 hours ago, JRBarrett said:

Some additional background on the TA/RA switch. (I am an avionics tech for a corporate jet operator).

As long as the transponder is in "standby" mode on the ground, it is OK to leave the TCAS set to TA/RA. The TCAS processor is a separate unit from the ATC transponder. It has two directional receiving antennas - one on top of the fuselage, and one below.

These antennas receive signals from the transponders of other other aircraft in flight, and the TCAS calculates the bearing, distance and relative altitude of airborne targets.

The TCAS has no transmitting ability on its own. In order to send interrogations to other aircraft (known as "squitter"), the TCAS uses the transmitter portion of the aircraft's transponder as its link to the outside world. As long as the transponder is selected to standby (either manually, or automatically via weight-on-wheels sensors), the TCAS cannot transmit.

In years past, it was always standard practice to place an aircraft's transponder in STBY mode as soon as exiting the runway after landing, and to not turn it on until entering the runway for takeoff.

Now, however, many large airports with heavy traffic volumes are equipped with surface detection radar known as ASDE-X, which permits ground controllers to see the exact positions of taxiing aircraft, even at night or in conditions of poor visibility. At such airports, all aircraft moving on taxiways are required to turn their transponders "on", so ground controllers can see them on ASDE-X.

In this situation, the pilot should turn the TCAS to STBY or OFF, to prevent it from sending squitter interrogations through the transponder, which could cause false TCAS alerts in other aircraft which are in the process of taking off or approaching for landing.

Many aircraft are equipped with ATC control panels which combine both TCAS and transponder control in a single rotary knob - with transponder modes coming first, followed by TCAS modes.

The control panel emulated in the IXEG 737 is one in which the transponder and TCAS mode selectors are separate.

 

Thought I knew about transponders and TCAS, see now I didnt so thank you for this information, highly valued.

So to sum up, the transponder in IXEG is set to Auto, does this mean its off on the ground and one should only set to stby when or if there is a ASDE-X function in use by direction of ATC?

[JRBarrett]

 

Thought I knew about transponders and TCAS, see now I didnt so thank you for this information, highly valued.

So to sum up, the transponder in IXEG is set to Auto, does this mean its off on the ground and one should only set to stby when or if there is a ASDE-X function in use by direction of ATC?

Yes, but don't confuse the function of the two switches. The 5-position switch on the left side marked OFF, TA, TA/RA, ABV, BLW controls the TCAS, which works WITH the transponder, but is not the transponder itself.

The transponder is controlled by the 3-position switch on the right side marked STBY, AUTO, ON.

When the transponder switch is in AUTO mode, it will not transmit on the ground. As long as the weight-on-wheels sensors on the landing gear detect that the aircraft is on the ground, the transponder remains in Standby. It will start transmitting the squawk code and aircraft altitude as soon as the aircraft becomes airborne.

In ON mode, the transponder is active no matter what the aircraft's air/ground status is. In STBY mode, the transponder remains off, even if airborne.

A summary of switch positions would be:

NON ASDE-X airport: Leave the TCAS switch at TA/RA, and the transponder switch at AUTO. (This is the IXEG default state). In this scenario, the transponder comes ON at takeoff, and goes into STBY on landing.

ASDE-X airport. Set the TCAS switch OFF, and the transponder switch ON, once pushback commences. When cleared for takeoff, switch the TCAS switch to TA/RA. Once airborne, you can switch the transponder from ON back to AUTO.

If landing at a NON-ASDE-X airport, just leave the switches in the default positions: TCAS at TA/RA, and transponder at AUTO.

If landing at an ASDE-X airport, switch the transponder from AUTO to ON at some point before touchdown. After landing, and after exiting the runway, leave the transponder ON, but turn the TCAS to off. Once parked at the gate and shutdown, go back to default positions: transponder to AUTO and TCAS back to TA/RA.

Of course, X-Plane airports don't actually have ASDE-X, so for the majority of users, just leave the TCAS and transponder switches at their default positions. The above techniques are really only for those who want to practice real-world procedures with 100% accuracy.

If you want to know if a particular airport has ASDE-X, you can download the r/w airport taxi diagram from a place like SkyVector. If ASDE-X is in use, there will be a note on the chart instructing pilots to turn transponders ON while taxiing.

[Dhruv]

In the US the AIM now recommends transponders set to ON/ALT while on all movement areas, ASDE-X or not.

[Tom Knudsen]

Thanks for the extra information, i do however believe that in Norwegian they did set transponder to on before entering the runway and of immidiate after exiting. Need to check that with a friend that flew Norwegians 737-300