I was on a UA 787-10 recently ORD-LAX sitting 47J. There was a very pronounced coarse vibration I could feel in my feet the entire trip. I've probably had maybe a dozen+ flights in UA 788/9 and two AA 788s and usually sit in Y somewhere and never felt anything as strong as this in my feet. These prevous 787 flights have been mostly transatlantic flights so I had ample opportunity to notice such things. I was on an A320, 739 and a 772 and a CRJ200 the rest of my recent trip this time and that 78X was vibrating my feet more than any of the other planes except the CR which only did so at certain times of the flight. Is that peculiar to the -10? All planes have some vibration you can feel in your feet, leaning on the side wall etc, sometimes its seems stronger depending on engine and I think flap settings/gear down etc but strong vibrations don't last too long. This one was the whole 4 hours continuously!! I didnt pay attention taxiing out but it was there taxiing in so its probably not related to actual flying conditions??? And this was much stronger than anything I can remember . Was this something specific to my location in the cabin or to the -10?? Or maybe the frequency made its amplitude seem higher??? Was I sitting in a simple harmonic motion anti node?? What causes it??

The 787 is much closer to a more-electric aircraft than most other models. This means that rather than distributing power in the form of bleed air or hydraulics, it distributes electricity from the much more powerful engine generators, to numerous electric devices running throughout the aircraft.

This is more efficient from a weight and performance perspective, but it also means more motors and other stuff operating throughout the flight. Also somewhat more reliance on the APU. Any of those things could produce some vibration, it you are sitting close to them.

Avatar2go wrote:

The 787 is much closer to a more-electric aircraft than most other models. This means that rather than distributing power in the form of bleed air or hydraulics, it distributes electricity from the much more powerful engine generators, to numerous electric devices running throughout the aircraft.

This is more efficient from a weight and performance perspective, but it also means more motors and other stuff operating throughout the flight. Also somewhat more reliance on the APU. Any of those things could produce some vibration, it you are sitting close to them.

Small correction. The 787 has no bleed air system, but it does have hydraulic systems for flight controls and landing gear.

I don't know if the architecture makes it more reliant on the APU than other aircraft of the same era (e.g. A350). Electric is normally generated by the engines either way. The APU is used for engine start but that's the same for other aircraft. The difference is that electrics are used to start the 787 engines as opposed to bleed air for other types.

Starlionblue wrote:

Small correction. The 787 has no bleed air system, but it does have hydraulic systems for flight controls and landing gear.

I don't know if the architecture makes it more reliant on the APU than other aircraft of the same era (e.g. A350). Electric is normally generated by the engines either way. The APU is used for engine start but that's the same for other aircraft. The difference is that electrics are used to start the 787 engines as opposed to bleed air for other types.

Yes, didn't mean to imply hydraulics were eliminated for control. It's a more-electric aircraft, not an all-electric aircraft. The main difference is the electrical power generation capability. Between engines and APU, 1.25 MVA of capacity is present on the aircraft, which is enormous.

Each engine has two 250 KVA generators, and the APU has two 125 KVA generators, which is double or more the level of other aircraft. They run a lot of loads that are usually handled in other ways.

https://www.designnews.com/boeings-more ... volution-0

Avatar2go wrote:

Any of those things could produce some vibration, it you are sitting close to them.

Generators, electric motors, hydraulic pumps and motors do in fact emit vibrations. But their frequency is usually too high to be felt as "strong vibration" in feet, arms or body. And I don't see why such vibration would be observed in a B787-10, but not in the -8 or -9.


Gruß, masi1157

masi1157 wrote:

Avatar2go wrote:

Any of those things could produce some vibration, it you are sitting close to them.

Generators, electric motors, hydraulic pumps and motors do in fact emit vibrations. But their frequency is usually too high to be felt as "strong vibration" in feet, arms or body. And I don't see why such vibration would be observed in a B787-10, but not in the -8 or -9.

I can't speak to the quality of the vibrations felt by another. He asked about possible sources so I pointed out that the 787 has more distributed electric machinery than most aircraft. Also pointed out that it would depend on where he was seated, which may vary between flights.

Avatar2go wrote:

I can't speak to the quality of the vibrations felt by another. He asked about possible sources so I pointed out that the 787 has more distributed electric machinery than most aircraft. Also pointed out that it would depend on where he was seated, which may vary between flights.

Sure, but those sources you mentioned are not likely to produce "strong vibrations" that he felt in his feet. Simply because their frequency is too high for that. You would much rather hear them than feel them.


Gruß, masi1157

masi1157 wrote:

Avatar2go wrote:

I can't speak to the quality of the vibrations felt by another. He asked about possible sources so I pointed out that the 787 has more distributed electric machinery than most aircraft. Also pointed out that it would depend on where he was seated, which may vary between flights.

Sure, but those sources you mentioned are not likely to produce "strong vibrations" that he felt in his feet. Simply because their frequency is too high for that. You would much rather hear them than feel them.

Have to respectfully disagree. I can certainly feel vibrations from window AC units, and older refrigerators. Anything with a compressor would have vibrational modes you could feel though solid objects. In addition there are resonances that can develop within structures and surfaces which amplify the sensation. Again we don't know what the OP felt, so very difficult to quantify.

Starlionblue wrote:

Avatar2go wrote:

The 787 is much closer to a more-electric aircraft than most other models. This means that rather than distributing power in the form of bleed air or hydraulics, it distributes electricity from the much more powerful engine generators, to numerous electric devices running throughout the aircraft.

This is more efficient from a weight and performance perspective, but it also means more motors and other stuff operating throughout the flight. Also somewhat more reliance on the APU. Any of those things could produce some vibration, it you are sitting close to them.

Small correction. The 787 has no bleed air system, but it does have hydraulic systems for flight controls and landing gear.

I don't know if the architecture makes it more reliant on the APU than other aircraft of the same era (e.g. A350). Electric is normally generated by the engines either way. The APU is used for engine start but that's the same for other aircraft. The difference is that electrics are used to start the 787 engines as opposed to bleed air for other types.

Small correction, the 787 does have a bleed air system...

'787 Engine Anti-Ice
General System Description
The EAI (Engine Anti-Ice) system uses engine compressor bleed air to heat the leading edge of the engine cowl to prevent ice from forming.'

Avatar2go wrote:

Have to respectfully disagree. I can certainly feel vibrations from window AC units, and older refrigerators. Anything with a compressor would have vibrational modes you could feel though solid objects. In addition there are resonances that can develop within structures and surfaces which amplify the sensation. Again we don't know what the OP felt, so very difficult to quantify.

The sources that you mentioned earlier are very well balanced and run at much higher frequency than your "old refrigerator". The sensitivity of the human body for vibration levels drops very fast with rising frequency. At appr. 1kHz you would hardly feel anything anymore. Therefore I find it very likely that the vibration, that the TO described as "strong" must have been at rather low frequency.

But you are right, as long as we don't know a bit more about that singular observation, it is all just "Kaffeesatzleserei" (I love the english translation "reading tea leafs", where we germans refer to coffee).


Gruß, masi1157

CALTECH wrote:

Small correction, the 787 does have a bleed air system...

'787 Engine Anti-Ice
General System Description
The EAI (Engine Anti-Ice) system uses engine compressor bleed air to heat the leading edge of the engine cowl to prevent ice from forming.'

Yes, this true, the 787 has a very small bleed air system for the immediate engine housing anti-icing. But the advantage of the more electric design is that it eliminates the traditional bleed air system that other aircraft have. And why it needs much greater generator capacity, to replace it.

Took a BA 787-10 flight from SEA to LHR some months back and was in 13A which is towards the front of the wing. As we got into cruise I noticed a really uncomfortable vibration cycle, similar to what I often feel on ships/ferries as best I can describe it. It was over about 8s or so as I remember, it would slowly build and then dissipate. I sucked it up for a bit trying to ignore it but it was quite intense. Hoped it would subside as we stepped up a cruise level - can’t remember if we didn’t change level or changing level didn’t change it but was very tired and had had enough at this point. Fortunately the flight wasn’t full so I went and slept in 16A where it wasn’t so noticeable. Told cabin crew lead and he sat down for a minute and said it was very noticeable and would report it. Can best be described as a throbbing cycle from the engine, which row 13 is directly opposite.

I would actively avoid sitting in this area in future, it was really uncomfortable.

chimborazo wrote:

As we got into cruise I noticed a really uncomfortable vibration cycle, similar to what I often feel on ships/ferries as best I can describe it. It was over about 8s or so as I remember, it would slowly build and then dissipate.

That is what is called beating in acoustics. You need 2 noise/vibration sources emitting very similar but not identical frequencies. You would then observe a tone at the average of the 2 frequencies, oscillating at the difference of the 2 frequencies. Considering where you were sitting it was most probably the engines' N1.

I don't know how it is done at Boeing, but at Airbus you can have a setting where both engines produce exactly the same thrust, but running at very slightly different speeds. Which results in exactly the described phenomenon.


Gruß, masi1157

Starlionblue wrote:

Avatar2go wrote:

The 787 is much closer to a more-electric aircraft than most other models. This means that rather than distributing power in the form of bleed air or hydraulics, it distributes electricity from the much more powerful engine generators, to numerous electric devices running throughout the aircraft.

This is more efficient from a weight and performance perspective, but it also means more motors and other stuff operating throughout the flight. Also somewhat more reliance on the APU. Any of those things could produce some vibration, it you are sitting close to them.

Small correction. The 787 has no bleed air system, but it does have hydraulic systems for flight controls and landing gear.

I don't know if the architecture makes it more reliant on the APU than other aircraft of the same era (e.g. A350). Electric is normally generated by the engines either way. The APU is used for engine start but that's the same for other aircraft. The difference is that electrics are used to start the 787 engines as opposed to bleed air for other types.

If I remember correctly from training. the 787 APU can be run for the entire trip in flight if one of the other generators has failed. I 've never seen the -10 in person so what you felt I cannot speak to though it probably has some merit.

strfyr51 wrote:

Starlionblue wrote:

Avatar2go wrote:

The 787 is much closer to a more-electric aircraft than most other models. This means that rather than distributing power in the form of bleed air or hydraulics, it distributes electricity from the much more powerful engine generators, to numerous electric devices running throughout the aircraft.

This is more efficient from a weight and performance perspective, but it also means more motors and other stuff operating throughout the flight. Also somewhat more reliance on the APU. Any of those things could produce some vibration, it you are sitting close to them.

Small correction. The 787 has no bleed air system, but it does have hydraulic systems for flight controls and landing gear.

I don't know if the architecture makes it more reliant on the APU than other aircraft of the same era (e.g. A350). Electric is normally generated by the engines either way. The APU is used for engine start but that's the same for other aircraft. The difference is that electrics are used to start the 787 engines as opposed to bleed air for other types.

If I remember correctly from training. the 787 APU can be run for the entire trip in flight if one of the other generators has failed. I 've never seen the -10 in person so what you felt I cannot speak to though it probably has some merit.

It can be run the entire trip.

But if we want to get nitpicky, so can the APU on other aircraft.

trex8 wrote:

I was on a UA 787-10 recently ORD-LAX sitting 47J. There was a very pronounced coarse vibration I could feel in my feet the entire trip.

For what I know and from the seat plan around the 47J area there really aren't any major mechanical components that will directly cause vibration feeling or sound from underneath.

The major area for pumps are in the wheelwell area (PECS/ICS) and at the back of the aircraft (SCU pumps and waste tanks)

However the upper recirculation fan is at around that area so that maybe the cause.

If it's a real concern, I would recommend having a word with the cabin crew and see if they would put it down in the report.

(Although to be honest, most of these issues the airline would have a report from Boeing long before any real failure would start to occur....)

chimborazo wrote:

Took a BA 787-10 flight from SEA to LHR some months back and was in 13A which is towards the front of the wing. As we got into cruise I noticed a really uncomfortable vibration cycle, similar to what I often feel on ships/ferries as best I can describe it. It was over about 8s or so as I remember, it would slowly build and then dissipate. I sucked it up for a bit trying to ignore it but it was quite intense. Hoped it would subside as we stepped up a cruise level - can’t remember if we didn’t change level or changing level didn’t change it but was very tired and had had enough at this point. Fortunately the flight wasn’t full so I went and slept in 16A where it wasn’t so noticeable. Told cabin crew lead and he sat down for a minute and said it was very noticeable and would report it. Can best be described as a throbbing cycle from the engine, which row 13 is directly opposite.

I would actively avoid sitting in this area in future, it was really uncomfortable.

Sounds like beat frequency from two vibration sources. Given there are two pretty big engines...

Starlionblue wrote:

It can be run the entire trip.

But if we want to get nitpicky, so can the APU on other aircraft.

Do any airliners/bizjets that are still altitude restricted?

chimborazo wrote:

Took a BA 787-10 flight from SEA to LHR some months back and was in 13A which is towards the front of the wing. As we got into cruise I noticed a really uncomfortable vibration cycle, similar to what I often feel on ships/ferries as best I can describe it. It was over about 8s or so as I remember, it would slowly build and then dissipate. I sucked it up for a bit trying to ignore it but it was quite intense. Hoped it would subside as we stepped up a cruise level - can’t remember if we didn’t change level or changing level didn’t change it but was very tired and had had enough at this point. Fortunately the flight wasn’t full so I went and slept in 16A where it wasn’t so noticeable. Told cabin crew lead and he sat down for a minute and said it was very noticeable and would report it. Can best be described as a throbbing cycle from the engine, which row 13 is directly opposite.

I would actively avoid sitting in this area in future, it was really uncomfortable.

oh good Im not going totally crazy!

rjsampson wrote:

Starlionblue wrote:

It can be run the entire trip.

But if we want to get nitpicky, so can the APU on other aircraft.

Do any airliners/bizjets that are still altitude restricted?

Probably.

Also, you have to more closely define "altitude restricted". For example, on the A330, you can run the APU the whole flight and it will provide electrical power. However, it won't provide bleed air above 25000 feet.

Starlionblue wrote:

rjsampson wrote:

Starlionblue wrote:

It can be run the entire trip.

But if we want to get nitpicky, so can the APU on other aircraft.

Do any airliners/bizjets that are still altitude restricted?

Probably.

Also, you have to more closely define "altitude restricted". For example, on the A330, you can run the APU the whole flight and it will provide electrical power. However, it won't provide bleed air above 25000 feet.

737 is a similar limitation. The 747 I think you can run it in flight but it can only be started on the ground

There have been some reports of vibration in 787-10, also prompting emergency landing. For example a United 787-10 returned to AMS due to vibrations: https://www.aeroinside.com/14714/united ... vibrations

All 787-10 have been manufactured at CHS where quality issues in 787 assembly occurred. Could the vibrations possible be related to the shimming requirements were not met during the assembly of certain structural joints. It is well known this can result in reduced fatigue thresholds and cracking of some structural joints, but could it also mean vibrations?

I think there is more to the 787 saga. All those flying 787 need to be checked in the same manner as all new delivered 787, especially the 787-10.

reidar76 wrote:

There have been some reports of vibration in 787-10, also prompting emergency landing. For example a United 787-10 returned to AMS due to vibrations: https://www.aeroinside.com/14714/united ... vibrations

All 787-10 have been manufactured at CHS where quality issues in 787 assembly occurred. Could the vibrations possible be related to the shimming requirements were not met during the assembly of certain structural joints. It is well known this can result in reduced fatigue thresholds and cracking of some structural joints, but could it also mean vibrations?

I think there is more to the 787 saga. All those flying 787 need to be checked in the same manner as all new delivered 787, especially the 787-10.

AVHerald shows that vibration occurs in many flight incidents, so not exclusive to the 787.

The 787 issues with shimming & joint mating affect the aircraft fatigue life, because the joints are able to flex a few thousandths of an inch more than the specifications allow, during each flight cycle. Additionally the fuselage stress is not evenly distributed across the joint. The impact of that behavior builds up over many thousands of flight cycles. It's not something that would lead to vibration, or even be detectable outside of specialized inspection.

The FAA did not issue a 787 airworthiness directive for those issues, allowing Boeing and the airlines to address the fleet during routine inspection and maintenance checks. That would not be the case if it caused vibration in flight.

trex8 wrote:

I was on a UA 787-10 recently ORD-LAX sitting 47J. There was a very pronounced coarse vibration I could feel in my feet the entire trip. I've probably had maybe a dozen+ flights in UA 788/9 and two AA 788s and usually sit in Y somewhere and never felt anything as strong as this in my feet. These prevous 787 flights have been mostly transatlantic flights so I had ample opportunity to notice such things. I was on an A320, 739 and a 772 and a CRJ200 the rest of my recent trip this time and that 78X was vibrating my feet more than any of the other planes except the CR which only did so at certain times of the flight. Is that peculiar to the -10? All planes have some vibration you can feel in your feet, leaning on the side wall etc, sometimes its seems stronger depending on engine and I think flap settings/gear down etc but strong vibrations don't last too long. This one was the whole 4 hours continuously!! I didnt pay attention taxiing out but it was there taxiing in so its probably not related to actual flying conditions??? And this was much stronger than anything I can remember . Was this something specific to my location in the cabin or to the -10?? Or maybe the frequency made its amplitude seem higher??? Was I sitting in a simple harmonic motion anti node?? What causes it??

Don't have much hands on the 787, but on the 787-10 the 2 Center Hydraulic Electric Motor Pumps are located in that area, left side under the Wing To Body Fairing, both C1 and C2 mounted to the fuselage.
They provide hydraulics to flight controls, different PCUs than the Left and Right Systems. Ailerons, Elevators, Rudder, Spoilers and Flaperons.
One pump would be primary, the other would be demand, They or one would be on the entire trip...
More than likely the vibration....

Right in the area you were sitting. Believe the removed panel above the two in dark shirts is where they are located...

Thanks Caltech. So maybe the 787 equivalent of the A320 dog bark on continuous!!

Shhh...it's all those gerbils on that really really loooong conveyor belt attached to the turbine shafts....

trex8 wrote:

Thanks Caltech. So maybe the 787 equivalent of the A320 dog bark on continuous!!

Seems to be...