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[LC0112G]

……….
Honestly, that boom on Saturday was the loudest sonic boom I've ever heard, and the house vibrated, like something heavy had hit it.  ………

My daughter said the same, although she’s in Bicester so not that far from you.

That's because this time they were quite low. Normally when they 'dash' from Coningsby to the south west, they climb to 41,000ft and then rip along over Oxford and Bristol before descending to intercept whatever it is. There isn't any commercial traffic up at FL410 so they get direct routing from air traffic control. Sonic booms at that altitude are usually like a loud rumble of thunder.

This time the 'intruder' had lost radio contact, and wasn't following it's flight plan. It was supposed to be going from Iceland to Southend, but deviated and went over Oxford and down towards Heathrow. The two Typhoons (Rigid 11 & 12) launched at about 13:05, and headed south, intercepting the 'intruder' just west of Heathrow. No way for ATC to clear the Typhoons through the busy London airspace and get them to climb to FL410 and then back down to FL140, so they stayed at medium altitude - which results in a very loud 'crack' of a sonic boom.

There is going to be a fuss about this one. Lost radio contact, then deviated from flight plan, and apparantly initially refused to follow instructions from the pilots of the QRA jets (to divert to Stansted) and tried to continue to Southend. Post 9/11 that's one way to get yourself shot down.

[Doctor Gollum]

A Canadair Dash8 on a delivery flight to darkest Africa with about 3 fuel stops apparently...

Large enough to be annoying but not large enough to make a big mess.

[TheBoy]

Dash-8's, they are the little twin prop puddle jumpers that Flybe used to take me Southampton<>Jersey IIRC?

[Doctor Gollum]

Dash-8's, they are the little twin prop puddle jumpers that Flybe used to take me Southampton<>Jersey IIRC?

Thems the ones

[TheBoy]

That's because this time they were quite low.

Thanks for the detailed explanation , much appreciated.

Why was the sound of the jets (assuming that was what I heard when I went out, after the sonic boom) sounding slow moving?  I've been up the side of big hills when Typhoons buzz through the valley, as the noise "moves" fast.  The noise of these jets sounded like it wasn't "moving" that fast across the sky....    ....unless they were so far in the distance by then, the noise was just coming from the same direction?

[LC0112G]

A Canadair Dash8 on a delivery flight to darkest Africa with about 3 fuel stops apparently...

Large enough to be annoying but not large enough to make a big mess.

Plenty big enough to cause significant casualties if you crash it into (say) Brent cross, or a packed football/rugby stadium. They could also improve LHR T5 by crashing into and demolishing it. During the Olympics we had QRA Typhoons intercepting Robinson R22 helicopters down here when they encroached on the sailing events in Portland harbour.

Ultimatley it doesn't matter if you're an A380 or a R22. You follow the rules, and if intercepted do what the fighters say, otherwise your day will get worse.

[Doctor Gollum]

That's because this time they were quite low.

Thanks for the detailed explanation , much appreciated.

Why was the sound of the jets (assuming that was what I heard when I went out, after the sonic boom) sounding slow moving?  I've been up the side of big hills when Typhoons buzz through the valley, as the noise "moves" fast.  The noise of these jets sounded like it wasn't "moving" that fast across the sky....    ....unless they were so far in the distance by then, the noise was just coming from the same direction?

Different sound frequency perhaps, but doesn't the sonic shock wave move with the aircraft whilst everything else is literally left in its wake

[Doctor Gollum]

A Canadair Dash8 on a delivery flight to darkest Africa with about 3 fuel stops apparently...

Large enough to be annoying but not large enough to make a big mess.

Plenty big enough to cause significant casualties if you crash it into (say) Brent cross, or a packed football/rugby stadium. They could also improve LHR T5 by crashing into and demolishing it. During the Olympics we had QRA Typhoons intercepting Robinson R22 helicopters down here when they encroached on the sailing events in Portland harbour.

Ultimatley it doesn't matter if you're an A380 or a R22. You follow the rules, and if intercepted do what the fighters say, otherwise your day will get worse.

Not disputing that, but it was probably being flown by the end user rather than a delivery crew from Canada, and whilst the rules should be the same globally, the interpretation and procedures can be somewhat variable.

However you spin it, one of those crashing, targeted or otherwise, is going to be much less of an event than a Korean Air Cargo 747 or similar. Like comparing a coach crash with a passenger train crash.

Nowhere to really shoot it down around Lundun either.

[LC0112G]

That's because this time they were quite low.

Thanks for the detailed explanation , much appreciated.

Why was the sound of the jets (assuming that was what I heard when I went out, after the sonic boom) sounding slow moving?  I've been up the side of big hills when Typhoons buzz through the valley, as the noise "moves" fast.  The noise of these jets sounded like it wasn't "moving" that fast across the sky....    ....unless they were so far in the distance by then, the noise was just coming from the same direction?

Not certain in this case, but when supersonic is authorised over land it's sometimes for just for one of the two QRA jets. That allows one of the jets to get into position quickly, whilst the other continues at subsonic speeds and arrives a few minutes later, but with a lot more fuel remaining.  So it's possible you heard the sonic boom from one jet, and then the 'normal' noise from the second jet.

Once the sonic boom has 'hit' you, you will continue to hear the jet as it heads away from you, and Mr Doppler says it will have a lower apparent frequency than a slower jet.

It appears the supersonic jet(s?) slowed down to subsonic as they crossed the M40 in the region of RAF Benson.

[LC0112G]

A Canadair Dash8 on a delivery flight to darkest Africa with about 3 fuel stops apparently...

Large enough to be annoying but not large enough to make a big mess.

Plenty big enough to cause significant casualties if you crash it into (say) Brent cross, or a packed football/rugby stadium. They could also improve LHR T5 by crashing into and demolishing it. During the Olympics we had QRA Typhoons intercepting Robinson R22 helicopters down here when they encroached on the sailing events in Portland harbour.

Ultimatley it doesn't matter if you're an A380 or a R22. You follow the rules, and if intercepted do what the fighters say, otherwise your day will get worse.

Not disputing that, but it was probably being flown by the end user rather than a delivery crew from Canada, and whilst the rules should be the same globally, the interpretation and procedures can be somewhat variable.

However you spin it, one of those crashing, targeted or otherwise, is going to be much less of an event than a Korean Air Cargo 747 or similar. Like comparing a coach crash with a passenger train crash.

Nowhere to really shoot it down around Lundun either.

The issue here is that it should have been going to Southend, which is east of London, and yet it somehow ended up west of London. Thats a big navigation error, and combined with loss of radio contact with ATC was always going end up with fighters on your tail. It was given the infamous "If you do not comply I am instructed by His Majesty's Government to shoot you down" command twice by the Typhoons on VHF Guard (121.5).

If you believe that it would not have been shot down due to it's location close to London, I'm afraid you're wrong. Perhaps pre 9/11, but not now. Attempting to go direct from LHR to Southend would take them right OTT central London. As it was they were ordered to turn north, and they passed over Northolt and Luton to Stansted.

[Doctor Gollum]

I never said they wouldn't shoot down a threat over Lundun, just that it wouldn't be ideal choice

[Marks DTM Calib]

Not certain in this case, but when supersonic is authorised over land it's sometimes for just for one of the two QRA jets. That allows one of the jets to get into position quickly, whilst the other continues at subsonic speeds and arrives a few minutes later, but with a lot more fuel remaining.  So it's possible you heard the sonic boom from one jet, and then the 'normal' noise from the second jet.

I did note that Brize threw a tanker up pretty quickly when the jets were scrambled

[Raeturbo]

Be prepared👍 comforting news that

[LC0112G]

Not certain in this case, but when supersonic is authorised over land it's sometimes for just for one of the two QRA jets. That allows one of the jets to get into position quickly, whilst the other continues at subsonic speeds and arrives a few minutes later, but with a lot more fuel remaining.  So it's possible you heard the sonic boom from one jet, and then the 'normal' noise from the second jet.

I did note that Brize threw a tanker up pretty quickly when the jets were scrambled

They always launch the "TANSOR" for a live QRA shout, assuming there isn't already a tanker airborne on training mission which can be diverted for the higher priority mission. They usually launch TANSOR for a practice shout too. It's quite often ZZ336, which is the specially painted "Boris 1" jet, because that sits on the ground waiting for its next VIP tasking, and so is 'available' for QRA shouts, whereas the others could be scheduled to go to Cyprus, the Falklands, or wherever.

Standard QRA procedure is to launch two Typhoons from either Coningsby (QRA-South) or Lossiemouth (QRA-North) and one Tanker (Tansor) from Brize. The tanker heads off to a suitable overwater refuelling area waiting for the Typhoons to show up. The two Typhoons then take turns shadowing the threat whilst the other goes off to the tanker for a top up. A single tanker can keep two Typhoons in the air for in excess of 10 hours if required.

Once the threat is over one Typhoon lands to be re-armed, serviced, refuelled, flush the loos, reload the egg sarnies etc, whilst the other stays airborne and alert with the tanker. Once the first jet is ready to resume QRA alert in it's shelter the second jet lands and is serviced in turn. This way there is always at least one armed jet ready to deal with a second 'threat' should there be two in close succession.

Finally, once the two QRA jets are back in their shelters and ready to go again if required, the Tanker pootles back to Brize for tea and medals.

The RAF/MOD never make it clear what the procedure is if more than 4 fighters (2 in Scotland, 2 in Lincolnsausageshire) are needed. Supposition is that the first 4 QRA jets are available in 15 minutes (typically more like 5 minutes) and another 4 can be generated in 30 minutes-1 hour. How that works in reality hasn't been tested recently though AFAIK. Can't see there being 8 pilots on duty on a bank holiday Sunday for instance.

[countrywoman]

Its surprising how far a sonic boom travels, when I lived just under the Malvern hills on the Worcestershire side like clockwork you could hear Concord giving it large over the Bristol channel.