So, two questions:

1. What are the ports around the A350's nose? There are three on the left, three on the right and I think two at the top
2. Why doesn't the 787 have them?

It honestly ruins the aircraft a bit for me as the positioning is kinda ugly.

Do you mean the two pitot tubes and one alpha vane on each side below the flight deck windows or the three static ports on each side aft of the cargo door?

The 787 has same type of sensors although the location is different.

I don't mind the pitot tubes, alpha vanes, and static ports as much as I dislike the "eyemask". B787 has a much more aesthetic treatment of the flight deck windows.

The ones in a vertical line below the cockpit window on the RHS, the top two are known as multi function probes, they provide total pressure, total temperature, and angle of attack in one sensor. Below that is an ice detector.

Below the cockpit window/wipers are three sideslip angle probes, on the test aircraft outside those on either side were additional total air temperature probes. They are not on production aircraft.

As to why they are not on the 787, they are covered by a patent.

zeke wrote:

The ones in a vertical line below the cockpit window on the RHS, the top two are known as multi function probes, they provide total pressure, total temperature, and angle of attack in one sensor. Below that is an ice detector.

Below the cockpit window/wipers are three sideslip angle probes, on the test aircraft outside those on either side were additional total air temperature probes. They are not on production aircraft.

As to why they are not on the 787, they are covered by a patent.

Thanks! So, what does the 787 use instead?

crimsonchin wrote:

zeke wrote:

The ones in a vertical line below the cockpit window on the RHS, the top two are known as multi function probes, they provide total pressure, total temperature, and angle of attack in one sensor. Below that is an ice detector.

Below the cockpit window/wipers are three sideslip angle probes, on the test aircraft outside those on either side were additional total air temperature probes. They are not on production aircraft.

As to why they are not on the 787, they are covered by a patent.

Thanks! So, what does the 787 use instead?

Individual probes that provide the same information with one function per probe.

crimsonchin wrote:

Thanks! So, what does the 787 use instead?

The 787 has six static ports, three pitot probes, and two angle–of–attack vane and one one total air temperature probe.

The 787 does not have the same amount of data coming into the Air Data Reference System as the A350 does, it also does not have the same system redundancy. The A350 basically has 3 independent primary systems plus another independent backup system, plus the ability to use the air data computers on each engine.

zeke wrote:

crimsonchin wrote:

Thanks! So, what does the 787 use instead?

The 787 has six static ports, three pitot probes, and two angle–of–attack vane and one one total air temperature probe.

The 787 does not have the same amount of data coming into the Air Data Reference System as the A350 does, it also does not have the same system redundancy. The A350 basically has 3 independent primary systems plus another independent backup system, plus the ability to use the air data computers on each engine.

This is fascinating to me, and as always some great insider information from you, Zeke!

Can you elaborate a little on the redundancy usage of the sensors, particularly the air data information obtained at the engine level?

Are you saying that in the event of some sort of pitot heat failure/ice (then again I imagine these multi-sensors are totally different in design) or ice-over, breaking off, whatever - of all three "multi" sensors, that the computers are actually capable of (and programmed to) use the remaining data from the engine system sensors to allow aircraft flight control computers to continue functioning? Does it retain any flight envelope protections? I'd imagine not at that point, with three systems already inop.

In any event, that's really impressive, and seems FAR beyond what would be expected during the design phase. Like someone came along one day and said, "hey, we've got the data the engines are using - it's basically what the flight control computers use too.. what if we made it available in case something ever happened."

estorilm wrote:

zeke wrote:

crimsonchin wrote:

Thanks! So, what does the 787 use instead?

The 787 has six static ports, three pitot probes, and two angle–of–attack vane and one one total air temperature probe.

The 787 does not have the same amount of data coming into the Air Data Reference System as the A350 does, it also does not have the same system redundancy. The A350 basically has 3 independent primary systems plus another independent backup system, plus the ability to use the air data computers on each engine.

This is fascinating to me, and as always some great insider information from you, Zeke!

Can you elaborate a little on the redundancy usage of the sensors, particularly the air data information obtained at the engine level?

Are you saying that in the event of some sort of pitot heat failure/ice (then again I imagine these multi-sensors are totally different in design) or ice-over, breaking off, whatever - of all three "multi" sensors, that the computers are actually capable of (and programmed to) use the remaining data from the engine system sensors to allow aircraft flight control computers to continue functioning? Does it retain any flight envelope protections? I'd imagine not at that point, with three systems already inop.

In any event, that's really impressive, and seems FAR beyond what would be expected during the design phase. Like someone came along one day and said, "hey, we've got the data the engines are using - it's basically what the flight control computers use too.. what if we made it available in case something ever happened."

Expanding on Zeke's post, A350 air data architecture and redundancy basically works like this. (Hoping I haven't missed anything.)

ADR (Air Data Reference) is part of the ADIRUs. ADIRUs 1, 2 and 3 each use one multifunction probe providing total pressure, total temperature and angle of attack, two static ports providing static pressure and one side slip angle probe. In addition, two OAT probes give static temp on the ground and during TO and landing. (OAT 1 gives data to ADIRU1, while OAT2 gives data to ADIRUs 2 and 3.)

A fourth AoA probe gives raw data AoA to the flight computers.

In normal operation, ADIRU 1 data is on the Captain's PFD, while ADIRU 2 data is on the F/O PFD.

If you lost 1, 2 or 3, you'd still have 2 independent "main" systems. If you lost two out of three, you'd still have one air "main" data system. Switching is automatic or manual.

If you lost all three systems, ISIS data would be used, and since the PRIMs have rejected all ADR data as invalid, flight control reverts to Direct Law. ISIS uses a standby pitot probe and two standby static probes. ISIS data is displayed on the standby instrument.

In case even ISIS is lost, air data from the engines is used. The engines have their own probes. As you can probably infer from the above, chances are slim of getting to this point.

crimsonchin wrote:

So, two questions:

1. What are the ports around the A350's nose? There are three on the left, three on the right and I think two at the top
2. Why doesn't the 787 have them?

It honestly ruins the aircraft a bit for me as the positioning is kinda ugly.

Positioning of the 330 probes is further back, which puts them in the areas where cargo loaders and airbridges are operating. This makes them more vulnerable to damage on the ground.

Marketing material aside, manufacturers don't design aircraft with aesthetic considerations as the main driver.

Starlionblue wrote:

estorilm wrote:

zeke wrote:

The 787 has six static ports, three pitot probes, and two angle–of–attack vane and one one total air temperature probe.

The 787 does not have the same amount of data coming into the Air Data Reference System as the A350 does, it also does not have the same system redundancy. The A350 basically has 3 independent primary systems plus another independent backup system, plus the ability to use the air data computers on each engine.

This is fascinating to me, and as always some great insider information from you, Zeke!

Can you elaborate a little on the redundancy usage of the sensors, particularly the air data information obtained at the engine level?

Are you saying that in the event of some sort of pitot heat failure/ice (then again I imagine these multi-sensors are totally different in design) or ice-over, breaking off, whatever - of all three "multi" sensors, that the computers are actually capable of (and programmed to) use the remaining data from the engine system sensors to allow aircraft flight control computers to continue functioning? Does it retain any flight envelope protections? I'd imagine not at that point, with three systems already inop.

In any event, that's really impressive, and seems FAR beyond what would be expected during the design phase. Like someone came along one day and said, "hey, we've got the data the engines are using - it's basically what the flight control computers use too.. what if we made it available in case something ever happened."

Expanding on Zeke's post, A350 air data architecture and redundancy basically works like this. (Hoping I haven't missed anything.)

ADR (Air Data Reference) is part of the ADIRUs. ADIRUs 1, 2 and 3 each use one multifunction probe providing total pressure, total temperature and angle of attack, two static ports providing static pressure and one side slip angle probe. In addition, two OAT probes give static temp on the ground and during TO and landing. (OAT 1 gives data to ADIRU1, while OAT2 gives data to ADIRUs 2 and 3.)

A fourth AoA probe gives raw data AoA to the flight computers.

In normal operation, ADIRU 1 data is on the Captain's PFD, while ADIRU 2 data is on the F/O PFD.

If you lost 1, 2 or 3, you'd still have 2 independent "main" systems. If you lost two out of three, you'd still have one air "main" data system. Switching is automatic or manual.

If you lost all three systems, ISIS data would be used, and since the PRIMs have rejected all ADR data as invalid, flight control reverts to Direct Law. ISIS uses a standby pitot probe and two standby static probes. ISIS data is displayed on the standby instrument.

In case even ISIS is lost, air data from the engines is used. The engines have their own probes. As you can probably infer from the above, chances are slim of getting to this point.

Thanks for the information, that's pretty amazing. For reference, how do the number of permissible failures/failure modes compare to their previous aircraft, and a modern Boeing like the 787?

Also, with such redundancy, what is the MEL dispatch for all of these sensors, or are they all required?

Thanks again.

For comparison, the 330 has only two "main" systems, Captain's and FO's. These have one pitot, two static ports, one AoA sensor and a TAT (total temp) probe each.

The standby system has a pitot, two static ports and an AoA probe. It gets TAT data from the Captain's TAT probe.

ADIRU 1 gets information from the Captain probes, ADIRU 2 from the FO probes and ADIRU 3 from the standby probes.

As you see there are two fewer layers of redundancy compared to the 350. There is no third "main" system and no fallback on engine air data. Furthermore, switching is manual, instead of automatic.

Starlionblue wrote:

For comparison, the 330 has only two "main" systems, Captain's and FO's. These have one pitot, two static ports, one AoA sensor and a TAT (total temp) probe each.

The standby system has a pitot, two static ports and an AoA probe. It gets TAT data from the Captain's TAT probe.

ADIRU 1 gets information from the Captain probes, ADIRU 2 from the FO probes and ADIRU 3 from the standby probes.

As you see there are two fewer layers of redundancy compared to the 350. There is no third "main" system and no fallback on engine air data. Furthermore, switching is manual, instead of automatic.

Thanks! Even for its time, that system seemed fairly full-proof. You knew I had to ask, but do you believe AF447 had any impact on a seemingly unusual effort to add multiple additional levels of redundancy to an already reliable system? It does actually seem like the sensors, and methodology in which the computers select, compare, and choose incoming data would have prevented such a scenario from playing out, even if multiple mistakes were made by flight crew.

Also last one (I suppose I should try to google some of this) - does the 380 feature the conventional sensor/computer setup or something more like the 350?

The A380, A400M, and A350 have similar avionics architecture.

estorilm wrote:

You knew I had to ask, but do you believe AF447 had any impact on a seemingly unusual effort to add multiple additional levels of redundancy to an already reliable system? It does actually seem like the sensors, and methodology in which the computers select, compare, and choose incoming data would have prevented such a scenario from playing out, even if multiple mistakes were made by flight crew.

There is little doubt in my mind that AF447 had an impact on design but I have a feeling it had more of an impact on awareness and training.

I wasn't a pilot at the time of AF447 (though several regular posters were), so I don't know how unreliable airspeed as an event was seen by flight ops and training departments at the time. Recognizing and taking correct action when faced with unreliable airspeed are emphasized in current training, at least where I work.