Heathrow closed all day Fri 21/3/25 - Aviation Impacts

[Dstock7080]

BA now trying to get passengers back for flights leaving this evening:
BA055 Johannesburg
BA057 Johannesburg
BA011 Singapore
BA259 Riyadh
BA045 Cape Town
BA059 Cape Town
BA015 Sydney via Singapore

 

[chiltern trev]

Heathrow have put out an announcement, and since are giving briefings and have the transport secretary doing similarly, which seem highly dubious and very much going on the offensive in response to criticism of their exposure to this not unforeseeable event. I find myself questioning the veracity of their claims.

Black swan incidents do happen from time to time, fallback systems fail, the perfect storm of issues coincides, and perhaps this is such an event – but I am also very interested in whether decision making arising from misaligned incentives (per Willie Walsh), "enterprise risk frameworks" and the impact of everything else that tries to squeeze the life out of hard engineering decisions so as to make them just another line item around a boardroom table.

I know as much as the next person on the decisions that led to this event, but the fact of the matter is that a single substation failure seems to have had cascading effects on the ability for a piece of "critical national infrastructure" to operate at all – and they didn't have any means to recover quickly. I don't see any other way to skin it.

It is rather frustrating when this quickly becomes a PR game of cover, deflect and pacify rather than accept, apologise and commit to better. This seems so prevalent in our services and institutions today (it is rare to ever receive an apology) and is a good reminder of how centralisation and standardisation reduces the resilience of a system in handling anomalous events without complete collapse.

Quoting from the piece in the press, with my commentary:


It's trivially possible for this to be true without it actually meaning much – are those supplies intended to be resilient and interchangeable, or separate supplies for separate purposes? The rail network could still operate through the site with traction feeders from elsewhere – satisfying the definition of "multiple sources".


Great – so this sort of confirms the above in that it's not intended as a redundant system ("a source is interrupted" => run on diesel). Safety of flight wasn't impacted, which everyone keeps reminding us about as if that should be a surprise, but the airport couldn't function effectively for a day.


Do they have multiple HV feeders, from separate sources, maybe connected in a ring, and N+1 or N+2 redundancy so they can lose one and still run the airport on full load? Apparently not, or at least they weren't working correctly.


Meaningless drivel about consuming as much energy as a small city, which seems to be intended to keep criticism at bay by some appeal to handwaving "it's complicated". Plenty of other energy demanding facilities (data centres, heck even actual urban areas) are typically capable of operating with loss of a single feeder...


It rather surprises me that, had this sort of eventuality been foreseen, this wasn't a tried, tested, practised and documented procedure such that it could have been implemented with far less time.

I will stand corrected if there are indeed legitimate reasons that, despite the above, things broke in unforeseen ways – but I hold my suspicions that some people may have egg on face today as a result of botched resilience arrangements or failure to adequately plan – with huge consequences for many travellers and employees.

From the BBC news at various times today, Heathrow is fed from ONE substation, the one that went on fire.

Various backup generators started up (i.e. presumed to be all the ones Heathrow has) but not enough coverage of Heathrow hence closure decision.

The question has to be asked, Why is Heathrow not fed from more than one major substation.

 

[baz962]

I wonder how many residents of Windsor, Hounslow and the Richmond area have overslept today…

A quick look suggests most Virgin and BA flights that were on the way to Heathrow have done a “Uey” and heading back to origin. A few have diverted - eg flights from Cape Town and Rio landing in Madrid.

I'm currently in Dallas. We were quite a few hours in before getting redirected back to Dallas last night.

 

[Nicholas Lewis]

Heathrow have put out an announcement, and since are giving briefings and have the transport secretary doing similarly, which seem highly dubious and very much going on the offensive in response to criticism of their exposure to this not unforeseeable event. I find myself questioning the veracity of their claims.

Black swan incidents do happen from time to time, fallback systems fail, the perfect storm of issues coincides, and perhaps this is such an event – but I am also very interested in whether decision making arising from misaligned incentives (per Willie Walsh), "enterprise risk frameworks" and the impact of everything else that tries to squeeze the life out of hard engineering decisions so as to make them just another line item around a boardroom table.

I know as much as the next person on the decisions that led to this event, but the fact of the matter is that a single substation failure seems to have had cascading effects on the ability for a piece of "critical national infrastructure" to operate at all – and they didn't have any means to recover quickly. I don't see any other way to skin it.

It is rather frustrating when this quickly becomes a PR game of cover, deflect and pacify rather than accept, apologise and commit to better. This seems so prevalent in our services and institutions today (it is rare to ever receive an apology) and is a good reminder of how centralisation and standardisation reduces the resilience of a system in handling anomalous events without complete collapse.

Quoting from the piece in the press, with my commentary:


It's trivially possible for this to be true without it actually meaning much – are those supplies intended to be resilient and interchangeable, or separate supplies for separate purposes? The rail network could still operate through the site with traction feeders from elsewhere – satisfying the definition of "multiple sources".


Great – so this sort of confirms the above in that it's not intended as a redundant system ("a source is interrupted" => run on diesel). Safety of flight wasn't impacted, which everyone keeps reminding us about as if that should be a surprise, but the airport couldn't function effectively for a day.


Do they have multiple HV feeders, from separate sources, maybe connected in a ring, and N+1 or N+2 redundancy so they can lose one and still run the airport on full load? Apparently not, or at least they weren't working correctly.


Meaningless drivel about consuming as much energy as a small city, which seems to be intended to keep criticism at bay by some appeal to handwaving "it's complicated". Plenty of other energy demanding facilities (data centres, heck even actual urban areas) are typically capable of operating with loss of a single feeder...


It rather surprises me that, had this sort of eventuality been foreseen, this wasn't a tried, tested, practised and documented procedure such that it could have been implemented with far less time.

I will stand corrected if there are indeed legitimate reasons that, despite the above, things broke in unforeseen ways – but I hold my suspicions that some people may have egg on face today as a result of botched resilience arrangements or failure to adequately plan – with huge consequences for many travellers and employees.

Well summed up. As minimum the DfT in conjunction with DENZ should have an independent investigation into this but no sign of that currently.

 

[chiltern trev]

https://www.ssen.co.uk/globalassets...egic-development-plan---for-consultation.pdfp

The sub station on fire is North Hyde Grid Supply Point which operates at voltages from 66kV down to LV. (I presume LV means circuits at voltage levels into houses, or voltage for a small substation that feeds houses directly).

North Hyde supplies a number of data centres. Looking at Google maps, it shows Ark Data Centres about 50m away, to the north on the other side of the Grand Union Canal. North Hyde Grid Supply point is on the south side of the Grand Union Canal, there being a small (40m?) plot of land in a cleared/derelict condition as though part of the sub station.

The above document is 44 pages long with many maps, diagrams and tables and has an issue date of Dec 2024.

North Hyde supplies Hillingdon, Hounslow, Ealing and Heathrow.

 

[Mogster]

I work for an NHS ALB, pharmaceuticals production. In case of power failure we have a backup generator that runs the whole site, all critical equipment is on UPS that covers switchover. The generator is tested monthly, powering the site for 3 hours. We have enough diesel on site for 7 days.

I know nothing about how a site like Heathrow is powered. However I find it baffling that Heathrow wouldn’t have some sort of power failure mitigation and it wasn’t regularly tested. It’s so bizarre that it makes me feel there’s something else going on other than a routine power failure. I realise that makes me sound like a tinfoil hatter…

 

[Bald Rick]

I'm currently in Dallas. We were quite a few hours in before getting redirected back to Dallas last night.

If you were on BA192, you turned back over Newfoundland!

 

[thejuggler]

Heathrow have put out an announcement, and since are giving briefings and have the transport secretary doing similarly, which seem highly dubious and very much going on the offensive in response to criticism of their exposure to this not unforeseeable event. I find myself questioning the veracity of their claims.

Black swan incidents do happen from time to time, fallback systems fail, the perfect storm of issues coincides, and perhaps this is such an event – but I am also very interested in whether decision making arising from misaligned incentives (per Willie Walsh), "enterprise risk frameworks" and the impact of everything else that tries to squeeze the life out of hard engineering decisions so as to make them just another line item around a boardroom table.

I know as much as the next person on the decisions that led to this event, but the fact of the matter is that a single substation failure seems to have had cascading effects on the ability for a piece of "critical national infrastructure" to operate at all – and they didn't have any means to recover quickly. I don't see any other way to skin it.

It is rather frustrating when this quickly becomes a PR game of cover, deflect and pacify rather than accept, apologise and commit to better. This seems so prevalent in our services and institutions today (it is rare to ever receive an apology) and is a good reminder of how centralisation and standardisation reduces the resilience of a system in handling anomalous events without complete collapse.

Quoting from the piece in the press, with my commentary:


It's trivially possible for this to be true without it actually meaning much – are those supplies intended to be resilient and interchangeable, or separate supplies for separate purposes? The rail network could still operate through the site with traction feeders from elsewhere – satisfying the definition of "multiple sources".


Great – so this sort of confirms the above in that it's not intended as a redundant system ("a source is interrupted" => run on diesel). Safety of flight wasn't impacted, which everyone keeps reminding us about as if that should be a surprise, but the airport couldn't function effectively for a day.


Do they have multiple HV feeders, from separate sources, maybe connected in a ring, and N+1 or N+2 redundancy so they can lose one and still run the airport on full load? Apparently not, or at least they weren't working correctly.


Meaningless drivel about consuming as much energy as a small city, which seems to be intended to keep criticism at bay by some appeal to handwaving "it's complicated". Plenty of other energy demanding facilities (data centres, heck even actual urban areas) are typically capable of operating with loss of a single feeder...


It rather surprises me that, had this sort of eventuality been foreseen, this wasn't a tried, tested, practised and documented procedure such that it could have been implemented with far less time.

I will stand corrected if there are indeed legitimate reasons that, despite the above, things broke in unforeseen ways – but I hold my suspicions that some people may have egg on face today as a result of botched resilience arrangements or failure to adequately plan – with huge consequences for many travellers and employees.

It is not possible to insure or mitigate for every single event. Cost benefit will always play a role. When did this last happen?

In reality there was some inconvenience for passengers which can be insured against and a contingency plan which looks to have worked well.

Heathrow response could be just two words. 'Nobody died'.

 

[sharpener]

Do they have multiple HV feeders, from separate sources, maybe connected in a ring, and N+1 or N+2 redundancy so they can lose one and still run the airport on full load? Apparently not, or at least they weren't working correctly.

I had always supposed this would be the usual practice.

Our village in rural Devon has more than one substation, they are all fed at ~22 kV from the villages on either side. AIUI this means it can withstand the loss of either supply. If one substation goes up in flames the houses supplied by it will be blacked out but the breakers should trip and so the losses limited to just those properties as the other s/stations will still be supplied from one direction or the other.

Whole cities are provided for in the same kind of fashion, divided into sections with multiple interconnections to make them resilient. Surprised to learn these principles do not seem to have applied to LHR.

 

[Nicholas Lewis]

It is not possible to insure or mitigate for every single event. Cost benefit will always play a role. When did this last happen?

In reality there was some inconvenience for passengers which can be insured against and a contingency plan which looks to have worked well.

Heathrow response could be just two words. 'Nobody died'.

A failure of an electrical infeed is a perfectly plausible scenario that should be protected against. A big signalling centre has at least three independent supplies plus would have a back up generator for such mission critical infrastructure. Heathrow should be similarly equipped. DfT and DENZ should be ordering an independent review of why Heathrow found itself in this position,

 

[JN114]

I expect not all the airport lost power; and the whole-airport closure was more about maintaining control of the situation on the ground than an inability to operate everything everywhere.

 

[sharpener]

I expect not all the airport lost power; and the whole-airport closure was more about maintaining control of the situation on the ground than an inability to operate everything everywhere.

It was quite late (? lunchtime) that BBC News were reporting Terminals 2 and 4 were still both without power. I would have guessed that for general loads (i.e. not safety systems, em. lighting etc) each terminal would be supplied at MV from multiple sources/directions rather like a factory or hospital or @Mogster's lab is, so giving them the opportunity to reconfigure and get the show back on the road.

As the initial problem arose when they could anticipate several hours with relatively few arrivals/departures in which to do this maybe the response was over-reaction bordering on panic. Sometimes emergency plans do not survive contact with reality. Sometimes ppl ignore what has been carefully planned and rehearsed and make it up as they go along.

But the previous big outages at NATS do not inspire much confidence, no point in having the technicians on call at home if in fact they need to be on site in order to do things that cannot be performed remotely. Even then it was all back up in a few hours though the knock-on cancellations were quite substantial.

0930 Saturday edited to add: Although it is not meant to be for non-railway-related discussion this thread has an authoritative-sounding explanation of the actual power supply arrangements.

 

[eoff]

I know nothing about how a site like Heathrow is powered. However I find it baffling that Heathrow wouldn’t have some sort of power failure mitigation and it wasn’t regularly tested. It’s so bizarre that it makes me feel there’s something else going on other than a routine power failure. I realise that makes me sound like a tinfoil hatter…

They do have mitigation.
They have backup generation for safety-critical aircraft operations.
They had a plan to reroute power if one of their feeder substations fails (presumably what they were doing all day on Friday). Perhaps that supply rerouting is somehting that can be done quicker, I don't know.

What they did was take a choice that losing a major part of the incomming natiional grid infrastructure at no notice for a significant time was a very low risk.
This is where it is not so clear to me but as far as I understand it the substation fire took out a secondary transformer which normally could have taken over from a fault situation.

There was also a report saying that the substation that failed was running over capacity due to a lot of new load in the area.

A data centre might have a UPS but it could be feeding critical infrastructure only or only be specified to run full load for a very short time.

 

[chiltern trev]

There was also a report saying that the substation that failed was running over capacity due to a lot of new load in the area.

A data centre might have a UPS but it could be feeding critical infrastructure only or only be specified to run full load for a very short time.

Is there a link to the above report?

I worked as an IT Infrastructure Project Manager - the computer rooms and data centres had 100% backup - UPS to cover the time for the onsite diesel generator(s) coming online. So all the servers, network, Comms etc was covered.

If a data centre does not have UPS then in my opinion it is not really a data centre.

 

[Snow1964]

There was also a report saying that the substation that failed was running over capacity due to a lot of new load in the area.

This might be the report you require, originally issued in 2022 with updates in 2023 & 2024. Basically says lack of electricity supply was holding back connections to 12,579 homes across 3 west London boroughs (Hillingdon, Hounslow, Ealing)

https://www.london.gov.uk/media/105111/download

(quite long so not quoting it), as it talks about 1MW ramping solutions, and other short term solutions to allow new connections, but also upgrade timelines at the 5 main west London area supply (Iver, Laleham, North Hyde, Willesden, Ealing) locations.

 

[eoff]

This was the other document I found yesterday which gave some information relevant to LHR...

https://www.ssen.co.uk/globalassets/about-us/dso/current-consultations/north-hyde-grid-supply-point---strategic-development-plan---for-consultation.pdf

3.2.2.
Heathrow Airport
Heathrow Airport is a strategic transport hub that is currently supplied by multiple GSPs in the area. As shown in Figure 3, North Hyde GSP supplies the area to the Northeast of the airport. There are also dedicated supplies to other parts of the Heathrow Airport site. SSEN work closely with Heathrow Airport to develop a co-ordinated strategic plan for their future needs, including decarbonisation. The impact of EVs traveling to Heathrow airport is explored in section 5.2.

I see that UK Power Networks has Heathrow as a case study for resilient power...

Providing 24/7/365 resilient power to a global transport hub requires continuous innovation and dedication. This means around-the-clock maintenance, repairs, and renewals to thousands of high voltage electrical substations, transformers, relays, and more than 600km of cables.

30 Years in Aviation: Heathrow

Celebrating 30 Years in Aviation with Heathrow Airport. Over three decades, our long-term partnership with Heathrow has remained a testament to collaboration and shared innovation when delivering airport excellence. From delivering Terminal 5 to attaining Carbon Trust Level 3, we have supported...

www.ukpowernetworksservices.co.uk

 

[chiltern trev]

What they did was take a choice that losing a major part of the incomming natiional grid infrastructure at no notice for a significant time was a very low risk.

Very low risk - yes. If you asked the grid supplier they would not guarrantee 100% uptim but you would bet a figure lig 99.99% (or thereabouts).

So one day it will go out.

The other side of any risk analysis is what is the 'damage' from loss of power including reputational damage.

I had some input in relocation hundreds of servers from a numebr of computer rooms (with 100% UPS and generators which were becoming end of life) to a new location - the requirement was 2 separate incoming sub station feeds, UPS, lots of generators, static switches, etc and delivering 2 seperate and independant power cords at each server in a cabinet (so an A and a B power rail in each cabinet). The new data centre location thus had power from 2 separate substations (probably of similar size and importance to North Hyde) with each incoming power feed capable of supporting the whole data centre on its own.

I know nothing about how a site like Heathrow is powered. However I find it baffling that Heathrow wouldn’t have some sort of power failure mitigation and it wasn’t regularly tested. It’s so bizarre that it makes me feel there’s something else going on other than a routine power failure. I realise that makes me sound like a tinfoil hatter…

Heathrow has grown over the years so perhaps a result of piecemeal growth, shoe horning into a site and not looking at the big overall Heathrow picture in terms of what happens if power fails?

There was also a report saying that the substation that failed was running over capacity due to a lot of new load in the area.

So if you run a substation over capacity, do you arrive at the scenario where a big oil filled transformer runs above its nominal rated specification (yes I know it will run above spec for awhile) long enough, then the transfomer eventually fails with an explosion and the oil goes up in flames. (Oil used as coolant, the transformers sits inside a metal box full of oil, the transformer heats up the oil, sets up convection currents and the oil rises, the oil then flows outside the box into the multple d shaped tubes on the outside that look like handles, which cool the oil which flows down the external tubes and back into the transfomer box at the bottom).

So do oil filled transformers have a bund around them like you need for fuel storage tanks? Probably not.

 

[sharpener]

So do oil filled transformers have a bund around them like you need for fuel storage tanks? Probably not.

Good question. I don't know for sure but I can't recall seeing them in the switchyards I go past, one is right next to where I often stop for lunch on a long journey so will look next time.

The reported 25,000 litres of transformer oil (25 cu m) is one heck of a lot. Pity pcbs turned out to be carcinogenic, as they were less flammable, don't know if they were used in xformers of this size.

 

[m0ffy]

So do oil filled transformers have a bund around them like you need for fuel storage tanks? Probably not.

Usually, yes, large transformers are bunded. The arrangements are a little more complicated, too - the coolers are usually an external radiator-type array and there are often pumps and fans to help keep everything cool on newer transformers.

I’d be interested to know about the power feed arrangements to your data centre - dual 132kV supplies from separate GSPs is incredibly unusual.

 

[stuving]

The Telegraph has reported: "Heathrow warned decade ago of relying on single power station". Obviously that's a headline, so what the report says is different. That's a live feed and has been updated, it was saying:

Heathrow airport and the Government were warned a decade ago that the airport was overly reliant on very limited sources of power from the National Grid to keep it functioning, it has emerged.

A report by a global planning and infrastructure consultancy identified “the key weakness” to the airport’s ability to operate as being its dependence on just three electricity substations.

These cannot replace each other without lengthy reconfiguration

When the North Hyde substation in Hayes exploded and went up in flames at 11.20pm on Thursday it plunged the entire airport into chaos, forcing the diversion of thousands of flights and leaving tens of thousands of passengers stranded.

It was precisely the nightmare scenario predicted in a report by Jacobs consultants in 2014, which assessed the operational risks faced by Europe’s busiest international hub.

As Heathrow’s operations began to return to normal following its reopening on Friday night, its chief executive placed the blame on the external power failure and said similar disruption could happen at other airports.

Thomas Woldbye said he is “personally quite proud” of how the airport responded to the power outage that brought all flights to a halt.

He added: “This situation was not created at Heathrow airport. It was created outside the airport and we had to deal with the consequences.”

The Jacobs report, published by the Government, warned: “Beyond the management of supply and grid services, which lie outside the airport’s control, the responsibility for managing electricity supply risk lies with the airport and businesses operating from the airport.”

It warned: “While some services can be temporarily supported with generator or battery backups, the key weakness is the main transmission line connections to the airport.

“Outages could cause disruption to passengers, baggage and aircraft handling functions and could require closure of areas of affected terminals and potentially the entire airport.

“Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to recover.”

By matching quotes I've located that report here - it was done for the extended northern runway proposal. But it's not exactly detailed; the relevant sections is (as OCRed; it can't be copied):

2.4 Utility Outages
2.4.1 Electricity

Electricity is a critical utility for the airport. Outages could cause disruption to passenger, baggage and aircraft handling functions and could require closure of areas of affected terminals or potentially the entire airport. Even a brief interruption to electricity supplies could have a long-lasting impact as systems can take time to
recover.

Beyond the management of supply and grid services, which lie outside the airport's control, the responsibility for managing electricity supply risk lies with the airport and businesses operating from the airport. While some services can be temporarily supported with generator or battery backups, the key weakness is the main transmission line connections to the airport.

Heathrow is equipped with on-site generation and appears to have resilient electricity supplies that are compliant with regulations and standards. Its new energy centre is a biomass heat and power plant that enables both the T5 and T2 terminal complexes to be heated and powered from the plant, and also to feed the local power grid to support demand from other users.

It is not unreasonable to assume that the expansion of the airport would be accompanied with additional provision of resilient supplies and back-up generation or uninterruptible power supplies to serve the additional facilities. These additions could potentially enhance the resilience of existing facilities.

While the expansion of Heathrow would increase the number of passengers and aircraft affected by any power outage, its current provision of on-site generation and other measures to ensure resilient supply appear to be adequate to enable the expanded airport to withstand and recover from interruptions to supply.

There is a mention of the biomass CHP plant, which must be the source of the comments about the airport relying on burning wood chippings. What strikes me is the lack of anything about using diversity of grid supplies, by switching between them. It's evidently not seen as a standard practice in the resilience consultancy business. There isn't even anything about about there being three grid supplies, despite the Telegraph's implied quotes.

If you skip through the whole set of summaries in the report for all the risks, you'll see that this particular loss of electricity event was just one possibility among several for electricity, and a much larger number in all. And I doubt if loss of power overnight was studied at all - the emphasis would most likely have been on coping with a worst-case scenario of total power loss (e.g. local grid collapse) with the airport in full operation, and how to manage all those passengers at various stages of their arrival or departure.

 

[Nicholas Lewis]

So do oil filled transformers have a bund around them like you need for fuel storage tanks? Probably not.

They had a bund around them extract from Google streetview

 

[Backroom_boy]

I'm travelling back from HK Saturday 21st. I'll let you know how I get on....

Was absolutely fine; but on a packed Elizabeth line train

 

[Nicholas Lewis]

Good to see that govt has tasked NESO to investigate what happened at Heathrow

https://www.gov.uk/government/news/neso-to-investigate-heathrow-power-loss

NESO’s investigation will support efforts to build a clear picture of the circumstances surrounding this incident and the UK’s energy resilience more broadly so that it’s prevented from ever happening again.

 

[eoff]

There have been wider scope reviews of resilitence but they only seem to concern issues down to regional level and ,as far as I can tell, are considering risks due to external events and not looking at those that might be due to failing aging infrastructure.

For example this policy paper:

The UK Government Resilience Framework: 2023 Implementation Update (HTML)

"We are living through dangerous and volatile times. The risks we face are more complex - and they are evolving faster - than ever. Over the last year, the ongoing Russian aggression in Ukraine, increased cyber-attacks, early examples of artificial intelligence being misused, and extreme weather conditions have shown us the wide-ranging and long-lasting impact such risks have across our society."...

The UK Government Resilience Framework: 2023 Implementation Update (HTML)

www.gov.uk

One of the documents referenced above is a National Risk Register with this goal in the introduction...

"By focusing on our collective resilience, we can
help the nation be more safe, more secure – and
in turn, more prosperous. This National Risk
Register plays a vital role in that process, allowing
us to build towards an even brighter future."

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1175834/2023_NATIONAL_RISK_REGISTER_NRR.pdf

 

[Nicholas Lewis]

This news report has a good view of the damaged transformer

https://apnews.com/video/aerials-sh...ks-out-power-d9d9475ff5b64c6a9596e8b1247d9a5e

 

[hwl]

I work for an NHS ALB, pharmaceuticals production. In case of power failure we have a backup generator that runs the whole site, all critical equipment is on UPS that covers switchover. The generator is tested monthly, powering the site for 3 hours. We have enough diesel on site for 7 days.

I know nothing about how a site like Heathrow is powered. However I find it baffling that Heathrow wouldn’t have some sort of power failure mitigation and it wasn’t regularly tested. It’s so bizarre that it makes me feel there’s something else going on other than a routine power failure. I realise that makes me sound like a tinfoil hatter…

Heathrow has grown over the years so perhaps a result of piecemeal growth, shoe horning into a site and not looking at the big overall Heathrow picture in terms of what happens if power fails?

All the newer feeds to Heathrow from the bulk supply point to the south and west are 33kV (e.g. covering T5, cargo area, maintenance hangers, jet fuel storage, fire station) , the two oldest including the one that failed was 22kV and the other 22kV had to be turned off to fight the fire.
Closer/within Heathrow the 33kV/22kV will all be stepped down relatively quickly to 11kV/6.6kV and then lower again and the lack of common voltage for cross feeds may have been an issue reducing flexibility and adding complexity.

Medium to long term the best solution would appear to be not having anything at Heathrow fed from North Hyde with new feeds being added from other locations with better resilience.

 

[ACDC]

Can Farnborough not handle any of these planes or Northolt?

 

[Watershed]

Can Farnborough not handle any of these planes or Northolt?

If a plane has declared an emergency, for example due to them beginning to eat into their 30 minute final reserve fuel, any airfield will be made available to them regardless of whether it's civil, military etc.

However neither airport would be suitable for large numbers of planned diversions as they simply don't have the passenger facilities to handle hundreds of people. They're intended for small numbers of people on private planes.

 

[Bald Rick]

Can Farnborough not handle any of these planes or Northolt?

Neither could manage the aircraft (short runways) nor the passengers (no terminal facilities of remotely sufficient size).

IIRC there is a story on the aviation thread about a large aircarft that landed erroneously at Northolt instead of Heathrow, and it had to be stripped right down almost to the airframe to become light enough to take off again with minimum fuel on full power.

 

[Deepgreen]

I noticed three consecutive empty BA transfer flights from Gatwick to Heathrow yesterday, including an A380. The odd transfer flight is not uncommon (usually B777-200ERs). This was the FR24 scene during the closure - eerily quiet over London.