STT delay due to 3' X3" deep "Pothole"

[Melax]

Today @ STT, most 757 were delayed several hours (US airways 1012 etc...) due to a small Pothole 1,000' beyond departure end of RWY 10, Why did it take so long to fix it, is there any patch product that can be applied instantly? I know those Pilots were not very happy, (Christmas eve)...

[Mad (Flt) Scientist]

Having seen how badly and quick attempts at "quick repairs" of potholes fare on city streets, I'd be nervous about a temporary repair on an airfield.

The only 'patches' I can think of are the military-style runway repair patches, and the cure would be almost as bad as the disease i suspect ...

[Melax]

As of 9:00pm (AST) the ATIS still says that the pothole is there !!

[Carrier]

Only one small pothole? These wimps should stay well clear of places like FZQA Lubumbashi!

[411A]

Hmmm, many years ago flying DC-3's ex-STT, I flew around the potholes...rather difficult in a largish jet, I suppose...:}

[merlinxx]

Lumbum is A POTHOLE!!!!!!

[A2QFI]

In the early days of Tomorrow's World I remember a clip whe somebody repaired a hole in a runway with some sort of Araladite and a jet in the background 5 miles finals to land and it all worked! Obviously not - I've never seen or heard of anything like it since!

[llondel]

So how much tarmac/concrete is there in a pothole 3ft square by 3 inches deep?

[Mad (Flt) Scientist]

3*3*1/4= 2.25 ft^3 @ c.145lb/ft^3 = about 350lbs

[llondel]

Ummmm, no. If there was any tarmac in it then it wouldn't be a hole. :}

[Sallyann1234]

Repairing a pothole is more than just adding material until the top is level.
If the surface has dropped then there must be compaction/movement underneath and this must be properly excavated and backfilled to an appropriate depth before the surface layer can be made good. Otherwise the 'repair' will be short-lived.

[Mad (Flt) Scientist]

http://www3.sympatico.ca/hmfcfan/images/doh.gif

http://www3.sympatico.ca/hmfcfan/images/slap.gif

edit: @llondel

[OverRun]

Had the same thing six weeks ago (different location). Key issues are to proof roll around the failure to see if the runway is solid or rotten, and to bring the surface to the condition and cleanness that is required for operations. This was on the outer part of the runway, so we could narrow the runway temporarily. The following is an extract from the report:

1628hrs. Call from Tower requesting as to whether Chief Groundsman is around. A large section of RWY bitumen surface approx 2m x 3m at about 3m in from the northern edge of RWY had lifted due to extraction of clay filler that was being applied during under-runway pipe jacking.

Aircraft traffic at that time was very light. Tower was advised of the situation. RFFS required to wash off the filler & silt component that had busted its way out of the bitumen surface. Contacted the Fire Commander at time 1636hrs (approx) who called in all crews to assist in the cleanup. Once cleaned off it was decided that a multi tyre roller would be required to flatten out the raised bitumen. Called in engineer and more maintenance staff.

Strength tests/proof rolling were made of the runway utilizing the 16 tonne multi wheel roller and heaviest fire truck on the outer surrounding area of lifted bitumen with no evidence of softness noted. After rolling the affected area it was decided to lift the bitumen surface off to assess the damage to the underneath.

Airline 737 and large GA aircraft arrived at about 1520hrs and advised of the damaged edge of RWY by tower. They landed without incident. Engineer met with the 2 Captains and showed them the section and location of the damaged portion of RWY surface. It was decided to reduce the RWY width from 45m to 30m. The 737 Captain asked for a dotted line to be marked 7.5m in from the northern edge of RWY from TWY Z to approx 20m west of the affected area. Following the departure of both aircraft, the bitumen was lifted and an assessment made to repair the affected area.

Groundstaff made up a cement stabilized truck load of gravel road base which was applied to the affected area. Prior to reinstatement works the filler and contaminated base course was removed from the RWY failure. Further scheduled 737s landed and departed without incident. Following compaction from both the 16t roller and fire truck, groundstaff gave the final patch a once over cut with the grader. It was then left till the following afternoon to dry out and was patched with cold mix asphalt by 1445hrs. Runway width then changed back to 45m

In terms of patching speed at civil airports, the options are:

Hot asphalt (BC or AC) – only if there is a plant nearby and it is operating. If you are that lucky (very lucky), then it is about 4 hours to get organised, mill out, patch and re-open.

Cold mix asphalt – some airports keep a stockpile of ‘patching’ cold mix asphalt. It isn’t very good for long term performance, but if that is available and there are maintenance staff around, about 2 hours to get organised, mill out, patch and re-open. Then often you have to come back in the few days, close the runway for another 2 hours, and rip out the patch and redo with hot asphalt.

Cement stabilised gravel - lab tests have shown that the cement stabilised material gets very good strength after 8 hours curing. If the patch needs to be topped with asphalt, then it is about 12 hours to get organised, patch, surface and re-open. Otherwise open as an unsealed (but bound) patch in about 8 hours.

In a flat blind panic (sorry I meant controlled emergency and it wasn’t our fault but was due to some military fast jet drivers who would rather fly than read NOTAMS), a hole can be patched temporarily with gravel and dirt and the runway opened in 10 minutes. The patched area is not suited to trafficking except in an emergency.

Finally, the runway needs an engineering assessment (and maybe some testing) to see if it was a runway pavement failure of the common street type, or due to some more sinister problem such as under-mining, collapsing soil, dolomitic subsidence, flooding, tunnelling, etc. Even, as I once found years ago, a runway had been extensively tunnelled and filled with explosives in the war so as to be able to destroy it in the event that the ‘other side’ captured the airport. One of the tunnels eventually collapsed under a civil 727 . . . .

[TheOddOne]

Cold mix asphalt – some airports keep a stockpile of ‘patching’ cold mix asphalt. It isn’t very good for long term performance, but if that is available and there are maintenance staff around, about 2 hours to get organised, mill out, patch and re-open.

OverRun,

Excellent post.

At LGW, we had stockpiles of cold mix asphalt and had tried various proprietary brands over the years. If the failure occurred on the main runway during Mon-Fri 0800-1600, we had a gang on site who would attend within 5 mins, say 10 mins for the repair, all done in 15 mins. A typical scenario would be - runway inspection (carried out every couple of hours) notes a centreline lighting fitting failing and in possible danger of lifting out under heavy jet suck/blast. Runway closed, ATC advised 30 min delay. Gang called to runway, fitting lifted out by electricians, replaced by about 50kg of cold asphalt, levelled off with a whacker plate, inspected, handed back to ATC as operational. Everyone pleased that runway opened quicker than estimate. This repair would normally last for 2-3 days of typical operation (say 2,000 movements) before an overnight permanent solution was organised.

At the weekends/night, the gang were contracted to be on 1 hour callout, but as most of the guys lived locally, usually 30 mins.

Closing and repairing this type of failure is usually much quicker all round than going into re-declaring distances or in the case of LGW, opening up the Northern Runway, which usually takes 1 hour from a standing start. It can be achieved much quicker, though, with co-operation form Handling Agents moving a/c infringing the sideslope etc.

Basically, the surface of the main runway at LGW was relatively recently resurfaced and whilst it may suffer from minor defects from time to time, is a very robust asset. Just as well, as it's the world's busiest single runway!

Very interesting story about what sounds like a 'moling' operation to lay ducting under the surface at KSTT. We did this exercise at LGW a few years ago for a new 33kv power intake, but went sufficiently deep so as not to interfere with the surface construction.

Cheers,
TheOddOne

[Melax]

@ STT, the 757 were delayed for 3 to 4 hours , no markers were put in place, pilots were trying to get reference points as to the "1200' " mark to land long. After numerous inquiries by pilots, the 757's took a rwy 28 departure (hills @ the end of rwy 10) with a tail wind. Things seems to work very slow here among other things!!. I'm just a Pilot not a runway expert but I Think That this event could have been handled much much better. (By the way the pot hole was 2' wide 3" deep and on the center line.) The ATIS was hilarious, I had to record it That reminds me long ago when ATIS in Nouakchott in Mauretania warned of herds of camels or other livestock on the Runway !!

[411A]

That reminds me long ago when ATIS in Nouakchott in Mauretania warned of herds of camels or other livestock on the Runway !!

They are still there...:}