View Full Version : Antiskid INOP on B737NG

5th Oct 2010, 04:01
On the 737NG, when the antiskid is INOP, TKOF is still allowed.
Landing is also allowed providing flaps 40 is used, and the landing distance is cheked according to the Advisory Information (PI-QRH). Even though it is not mentioned in the QRH NNC (ANTISKID INOPERATIVE).

Imagine now one engine fails on takeoff (past V1) or after.
One engine INOP requires a flap 15 landing. The same Advisory Information (PI-QRH) regarding landing distance with One ENG INOP includes Antiskid... if I am correct?

How can we solve this operational contradiction?
Manufacturer limitation somewhere (I did not find)?
Company limitations?
Another solution?

Thanks in advance for your comments.
Enjoy the day.

6th Oct 2010, 16:46

In the abnormal section of my NG (737-800W-SFP) Performance Handbook (For our company a flap 15 landing is an abnormal procedure although other carriers use flap 15 routinely.) I am given table labeled “Flap 15 Landing Runway Weight Limit (cfm56-726) Antiskid Operative". I enter this table with landing distance available and a pressure altitude. The table then provides me with a landing weight for both dry and wet runway conditions.

For example given an 8,000’ dry runway and a pressure altitude of 1,000’ I have a flap 15 landing weight limit of 186,100 lbs (above my maximum certified takeoff weight)

Also in the abnormal section of my Performance Handbook I have a table entitled “Flaps 15 Landing Weight Limit Adjustment Antiskid Inoperative (includes Auto-Spoiler INOPT)” Given the landing distance available and a pressure altitude the table provides weight penalties for both wet and dry runways. The penalty would be then applied to Flaps 15 landing distance data derived from the previously mentioned table.

For example given the same 8,000’ dry runway and a pressure altitude of 1,000 I have a penalty of (93.9).

Zero wind flap 15 landing weight for the given conditions is: 186.100 lbs.
My penalty for antiskid inoperative is: 93,900 lbs.
My zero wind flap 15 antiskid inoperative landing weight limit for the conditions becomes 92,200 lbs. {186,100 - 93,900 = 92,200}

Given an 11,000’ sea level wet runway the numbers look like this.
190.0 (71.6) = 118,400 lbs flap 15 antiskid inoperative landing weight.

So, I can dispatch with antiskid inoperative with the limitation to land flaps 40. However when I get airborne I lose an engine. Now I am forced into a flap 15 landing and my antiskid system is MEL’d inoperative. I go into my abnormal section of my NG Performance Handbook and look at two separate charts. The first chart gives me flap 15 landing data, the second chart gives me a penalty for antiskid inoperative (and auto spoiler inoperative), and I combine the two and come up with a landing weight for the conditions I am faced with.

I hope I have correctly understood your question and the above information is of some use to you.



8th Oct 2010, 03:15

Thanks for your quick reply.

First, I was offered an answer (from a colleague) which said that we still have full manual braking... and that will comply with any sort of requirements since the manual braking is stronger than any level of the autobraking system. If I may be agree about this last statement, I would have been happy with some sort of answer from the manufacturer, I could find it with your inputs.

Secondly, you help me to look at this in a different way. I was searching for landing distances as the PI-QRH.
Reading the document you have sent, redirect me to the field length limit concept. Thus, I have found in the FPPM a Landing field weight limit F15 graph based on anti-skid inoperative and manual speedbrakes. It is not a table, but that is the information I was looking for.

Again, thank you for your help, your time and your enthusiasm sharing your knowledge.

8th Oct 2010, 04:42
I’m glad the information was useful for you. You asked a great question; trying to respond drove me back into the books, and that’s a good thing.

Take care,


9th Oct 2010, 04:43
Hi Guys, interesting question indeed!
IMHO I think you mixed up a MEL question with an inflight emergency problem (engine failure).
Before departure you have to satisfy all MEL points, but after departure the MEL does not fully apply anymore.
So whatever happens after departure is an absolute different story, you cannot take into account all eventualities...then you have to think also about flap failure or losing the brakes completely :eek: